Remove more reserved identifiers (#6925)

include/SDL3/SDL_assert.h

@@ -51,7 +51,7 @@ assert can have unique static variables associated with it.
 /* Don't include intrin.h here because it contains C++ code */
     extern void __cdecl __debugbreak(void);
     #define SDL_TriggerBreakpoint() __debugbreak()
-#elif _SDL_HAS_BUILTIN(__builtin_debugtrap)
+#elif SDL_HAS_BUILTIN(__builtin_debugtrap)
     #define SDL_TriggerBreakpoint() __builtin_debugtrap()
 #elif (defined(__GNUC__) || defined(__clang__)) && (defined(__i386__) || defined(__x86_64__))
     #define SDL_TriggerBreakpoint() __asm__ __volatile__ ( "int $3\n\t" )