Added migration documentation for SDL_strtoll(), SDL_strtoull(), SDL_lltoa(), and SDL_ulltoa().

docs/README-migration.md

@@ -1732,6 +1732,8 @@ SDL3 attempts to apply consistency to case-insensitive string functions. In SDL2
 
 Please note that the case-folding technique used by SDL3 will not produce correct results for the "Turkish 'I'"; this one letter is a surprisingly hard problem in the Unicode world, and since these functions do not specify the human language in use, we have chosen to ignore this problem.
 
+SDL_strtoll(), SDL_strtoull(), SDL_lltoa(), and SDL_ulltoa() use long long values instead of 64-bit values, to match their C runtime counterparts.
+
 The following macros have been removed:
 * SDL_TABLESIZE() - use SDL_arraysize() instead