[compiler-rt] Remove mentions of AuroraUX in code comments and docs.

AuroraUX was an operating system project based on an OpenSolaris kernel
and an Ada userland.

There appear to be no public code or release available online anymore.
The project page on Wikipedia [1] was deleted in January 2012, and a news
item [2] from November 2012 has more details.

[1] https://en.wikipedia.org/w/index.php?title=Special:Log/delete&page=AuroraUX
[2] https://www.phoronix.com/scan.php?page=news_item&px=MTIyMTI

compiler-rt/lib/builtins/int_endianness.h

@@ -41,7 +41,7 @@
 #error "unknown endianness"
 #endif // !_LITTLE_ENDIAN
 
-#endif // Solaris and AuroraUX.
+#endif // Solaris
 
 // ..
 

compiler-rt/test/builtins/Unit/endianness.h

@@ -17,7 +17,7 @@
 #define _YUGA_BIG_ENDIAN    0
 #endif /* _BYTE_ORDER */
 
-#endif /* Solaris and AuroraUX. */
+#endif /* Solaris */
 
 /* .. */
 

compiler-rt/www/index.html

@@ -77,7 +77,7 @@
    <p><b>builtins</b> is known to work on the following platforms:</p>
    <ul>
    <li>Machine Architectures: i386, X86-64, SPARC64, ARM, PowerPC, PowerPC 64.</li>
-   <li>OS: AuroraUX, DragonFlyBSD, FreeBSD, NetBSD, OpenBSD, Linux, Darwin.</li>
+   <li>OS: DragonFlyBSD, FreeBSD, NetBSD, OpenBSD, Linux, Darwin.</li>
    </ul>
 
    <p>Most sanitizer runtimes are supported only on Linux x86-64. See tool-specific