This refactors FontManager to improve it in several ways:
1. Change all the dynamic memory management to use `new`, rather than mixing `new` and `vm_malloc`
2. Change the current font to use an index rather than a pointer
3. Take advantage of more C++11 features to avoid redundant lookups
4. Use case-insensitive name comparison
5. Avoid overflowing the `fnt->filename` field
6. Use `Warning` rather than `Error` in a non-critical error situation
`gr_get_string_size` takes a length parameter, but `split_str_once` was calling it with the position instead. This led to incorrect results occasionally. If the incorrect pixel width had the bad luck to be exactly equal to the remaining space, this would cause an infinite loop. This fixes the bug and adds a bunch of safeguards to prevent a similar situation in the future.
* Fix underline length calculation in message scrollback
* Use SCP_string for message source (which allows ships with long display names to work without crashing) and message text
* Upgrade assorted functions to work with SCP_string
This allows to use standard TrueType Fonts for text rendering in FSO. It uses the NanoVG library which provides the ability of drawing 2D shapes. This library is used for most 2D operations now and can also be used directly by using the PathRenderer class.
Mike Nelson