Have SDLWrap::AllocPalette allocate space for 256 colors by default

Source/dx.cpp

@@ -236,7 +236,7 @@ void dx_reinit()
 
 void InitPalette()
 {
-	Palette = SDLWrap::AllocPalette(256);
+	Palette = SDLWrap::AllocPalette();
 }
 
 void BltFast(SDL_Rect *srcRect, SDL_Rect *dstRect)

Source/storm/storm_svid.cpp

@@ -229,7 +229,7 @@ bool SVidPlayBegin(const char *filename, int flags)
 	    SVidWidth,
 	    SDL_PIXELFORMAT_INDEX8);
 
-	SVidPalette = SDLWrap::AllocPalette(256);
+	SVidPalette = SDLWrap::AllocPalette();
 	if (SDLC_SetSurfaceColors(SVidSurface.get(), SVidPalette.get()) <= -1) {
 		ErrSdl();
 	}

Source/utils/sdl_wrap.h

@@ -60,7 +60,7 @@ inline SDLTextureUniquePtr CreateTexture(SDL_Renderer *renderer, Uint32 format,
 }
 #endif
 
-inline SDLPaletteUniquePtr AllocPalette(int ncolors)
+inline SDLPaletteUniquePtr AllocPalette(int ncolors = 256)
 {
 	return SDLPaletteUniquePtr { NonNull(SDL_AllocPalette(ncolors)) };
 }