wikiheaders: Allow parts of the headers to be ignored.

The specific cases here were SDL_size_mul_overflow_builtin and
SDL_size_add_overflow_builtin, which are forced-inline symbols in
SDL_stdinc.h that have to exist, but aren't really part of the public API,
and thus shouldn't be exported as documentation.

include/SDL3/SDL_endian.h

@@ -238,8 +238,7 @@ SDL_FORCE_INLINE Uint32 SDL_Swap32(Uint32 x)
 #pragma intrinsic(_byteswap_uint64)
 #define SDL_Swap64(x) _byteswap_uint64(x)
 #elif defined(__i386__) && !HAS_BROKEN_BSWAP
-SDL_FORCE_INLINE Uint64
-SDL_Swap64(Uint64 x)
+SDL_FORCE_INLINE Uint64 SDL_Swap64(Uint64 x)
 {
     union {
         struct {