(Font) Stop the font renderers touching the filesystem

Follow-up to 76f8821, which moved the reads and the path lookups up
into font_renderer_create_default(). Two things were left behind.

First, the renderers still decided what to do by looking at the path.
stb branched on

    if (!font_path || !*font_path)

to choose its built-in glyphs, and freetype used the same test to pick
the WiiU shared font. Neither reads a file any more, so the path says
nothing about whether a font actually arrived - font_data does. Branch
on that instead. stb no longer looks at font_path at all and gains a
fallback it did not have: a path that exists but cannot be read now
yields the built-in glyphs rather than failing outright, because the
decision is made on what turned up rather than on what was asked for.

freetype's fontconfig test keeps the path, and should: "fallback" is a
property of the font that was requested, not of whether a file was
found. Only the !*font_path half becomes a byte check.

That also exposed a leak. When fontconfig takes over - because nothing
was read, or because a fallback font was asked for - it supplies its
own bytes, and whatever font_renderer_create_default() had already
read was neither stored nor released. At 2.5 MB for a typical asset
font that is worth having back. Ownership passes to the renderer on
that path too, so it frees them.

Second, file/file_path.h was still included by all three renderers and
used by none - the only remaining mention was in a comment. stb also
kept streams/file_stream.h after its last read went away. Remove them.
The point is not the include lines: while those headers are present
the renderers are still nominally bound to the filesystem, and a path
lookup can creep back in without anyone noticing. Now it would not
compile.

streams/file_stream.h stays in freetype for the one read left, in the
fontconfig branch. Removing that one needs an interface change rather
than a hoist: fontconfig resolves a face index as well as a path
(FC_INDEX, which matters for TrueType collections - CJK system fonts
in particular), and it resolves against the requested font and the
user's locale, so a static candidate list cannot answer it. It means
threading a requested path into the resolver and a face index back out
to init().

stb, freetype and font_driver compile clean under
-Wdeclaration-after-statement. The CoreText change and both WiiU
branches are unbuildable here; all three are mechanical.

gfx/drivers_font_renderer/coretext.c

@@ -32,7 +32,6 @@
 #include <ApplicationServices/ApplicationServices.h>
 #endif
 
-#include <file/file_path.h>
 
 #include "../font_driver.h"
 

gfx/drivers_font_renderer/freetype.c

@@ -22,7 +22,6 @@
 
 #include <ft2build.h>
 
-#include <file/file_path.h>
 #include <streams/file_stream.h>
 #include <retro_miscellaneous.h>
 #include <string/stdstring.h>
@@ -406,7 +405,8 @@ static void *font_renderer_ft_init(const char *font_path,
       goto error;
 
 #ifdef WIIU
-   if (!*font_path)
+   /* No bytes arrived, so use the OS shared font. */
+   if (!font_data_in)
    {
       void* font_data         = NULL;
       uint32_t font_data_size = 0;
@@ -421,9 +421,18 @@ static void *font_renderer_ft_init(const char *font_path,
    }
    else
 #elif defined(HAVE_FONTCONFIG_SUPPORT)
-   /* if fallback font is requested, instead of loading it, we find the full font in the system */
-   if (!*font_path || strstr(font_path, "fallback"))
+   /* If no bytes arrived, or a fallback font was asked for, look the
+    * real font up in the system instead. The path is consulted here
+    * because "fallback" is a property of what was requested, not of
+    * whether a file was found. */
+   if (!font_data_in || (font_path && strstr(font_path, "fallback")))
    {
+      /* fontconfig supplies its own bytes, so release anything the
+       * caller read for us rather than holding it for the lifetime of
+       * the font. Ownership passed to us either way. */
+      free(font_data_in);
+      font_data_in = NULL;
+
       FcValue locale_boxed;
       uint8_t* font_data     = NULL;
       int64_t font_data_size = 0;
@@ -602,7 +611,7 @@ static const char * const *font_renderer_ft_get_default_fonts(void)
    return none;
 #else
    /* Selection happens in font_renderer_create_default(), which is
-    * what keeps path_is_valid() out of this file. */
+    * what keeps path lookups out of this file. */
    return font_paths;
 #endif
 }

gfx/drivers_font_renderer/stb.c

@@ -20,8 +20,6 @@
 #include <math.h>
 #include <stdint.h>
 
-#include <file/file_path.h>
-#include <streams/file_stream.h>
 #include <string/stdstring.h>
 #include <retro_miscellaneous.h>
 
@@ -1644,6 +1642,9 @@ static void *font_renderer_stb_init(const char *font_path,
    stb_font_renderer_t *self =
       (stb_font_renderer_t*)calloc(1, sizeof(*self));
 
+   /* font_path is unused: what matters is whether bytes arrived. */
+   (void)font_path;
+
    if (!self || font_size < 1.0f)
       goto error;
 
@@ -1652,7 +1653,7 @@ static void *font_renderer_stb_init(const char *font_path,
    font_size = -font_size;
 
 #ifdef WIIU
-   if (!*font_path)
+   if (!font_data)
    {
       uint32_t size = 0;
       /* OS-owned shared memory: borrowed, not owned - must not be freed. */
@@ -1663,19 +1664,19 @@ static void *font_renderer_stb_init(const char *font_path,
    }
    else
 #endif
-   if (!font_path || !*font_path)
+   if (!font_data || !font_data_len)
    {
-      /* No TrueType font was found; use the built-in glyphs. */
+      /* Nothing was loaded for us - either no candidate existed or it
+       * could not be read - so fall back to the built-in glyphs. The
+       * path is not consulted: this renderer does no file I/O, so the
+       * bytes are the only thing that says whether a font arrived. */
       if (!font_renderer_stb_init_builtin(self, -font_size))
          goto error;
       return self;
    }
    else
    {
-      /* Bytes come from font_renderer_create_default(); this renderer
-       * does no file I/O. Ownership transfers on success. */
-      if (!font_data || !font_data_len)
-         goto error;
+      /* Ownership transfers on success. */
       self->font_data       = font_data;
       self->font_data_size  = font_data_len;
       self->font_data_owned = true;