Fix SDL_memcmp argument mismatch in SDL_ttf.c

[stjepano]

Corrected the SDL_memcmp function to compare the 'string' argument instead of 'text', ensuring proper string comparison logic. This resolves potential functional issues caused by the incorrect argument usage.

Before the fix:

// init code
TTF_Text* Txt = TTF_CreateText(SomeTextEngine, SomeFont, "0", 1);
// ... change the text
TTF_SetTextString(Txt, "1", 1)
Assert( StrCmp(Txt->text, "1") == 0 ) // <-- this fails, Txt->text remains "0" 

After the fix:

// init code
TTF_Text* Txt = TTF_CreateText(SomeTextEngine, SomeFont, "0", 1);
// ... change the text
TTF_SetTextString(Txt, "1", 1)
Assert( StrCmp(Txt->text, "1") == 0 ) // <-- OK, Txt->text is "1"

[slouken]

Good fix, thanks!