We used 16-bit variables to store the 'character code' everywhere but
this won't let us represent anything beyond U+FFFF.
This patch changes those variables to a custom type that can be 32 or 16
bits depending on the build, and adjusts numerous internal APIs and
datastructures to match. This includes:
* utf8decode() and friends
* on-screen keyboard
* font manipulation, caching, rendering, and generation
* VFAT code parses and generates utf16 dirents
* WIN32 simulator reads and writes utf16 filenames
Note that this patch doesn't _enable_ >16bit unicode support; a followup
patch will turn that on for appropriate targets.
Known bugs:
* Native players in 32-bit unicode mode generate mangled filename
entries if they include UTF16 surrogate codepoints. Root cause
is unclear, and may reside in core dircache code.
Needs testing on:
* windows simulator (16bit+32bit)
Change-Id: I193a00fe2a11a4181ddc82df2d71be52bf00b6e6
d05c59f35b