error: SDL's allocators now call SDL_OutOfMemory on error.

This means the allocator's caller doesn't need to use SDL_OutOfMemory directly
if the allocation fails.

This applies to the usual allocators: SDL_malloc, SDL_calloc, SDL_realloc
(all of these regardless of if the app supplied a custom allocator or we're
using system malloc() or an internal copy of dlmalloc under the hood),
SDL_aligned_alloc, SDL_small_alloc, SDL_strdup, SDL_asprintf, SDL_wcsdup...
probably others. If it returns something you can pass to SDL_free, it should
work.

The caller might still need to use SDL_OutOfMemory if something that wasn't
SDL allocated the memory: operator new in C++ code, Objective-C's alloc
message, win32 GlobalAlloc, etc.

Fixes #8642.

src/thread/pthread/SDL_sysmutex.c

@@ -46,8 +46,6 @@ SDL_Mutex *SDL_CreateMutex(void)
             SDL_free(mutex);
             mutex = NULL;
         }
-    } else {
-        SDL_OutOfMemory();
     }
     return mutex;
 }

src/thread/pthread/SDL_sysrwlock.c

@@ -41,8 +41,6 @@ SDL_RWLock *SDL_CreateRWLock(void)
             SDL_free(rwlock);
             rwlock = NULL;
         }
-    } else {
-        SDL_OutOfMemory();
     }
     return rwlock;
 }

src/thread/pthread/SDL_syssem.c

@@ -48,8 +48,6 @@ SDL_Semaphore *SDL_CreateSemaphore(Uint32 initial_value)
             SDL_free(sem);
             sem = NULL;
         }
-    } else {
-        SDL_OutOfMemory();
     }
     return sem;
 }