Shut up some warnings

src/Draw.cpp

@@ -80,11 +80,15 @@ BOOL Flip_SystemTask()
 
 BOOL StartDirectDraw(int lMagnification, int lColourDepth)
 {
+	(void)lColourDepth;
+
 	//Initialize rendering
 	SDL_InitSubSystem(SDL_INIT_VIDEO);
 	
 	//Create renderer
-	if (gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED))
+	gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED);
+
+	if (gRenderer != NULL)
 	{
 		switch (lMagnification)
 		{

src/Font.cpp

@@ -223,7 +223,7 @@ void DrawText(FontObject *font_object, SDL_Surface *surface, int x, int y, unsig
 			const int letter_x = x + pen_x + face->glyph->bitmap_left;
 			const int letter_y = y + ((FT_MulFix(face->ascender, face->size->metrics.y_scale) - face->glyph->metrics.horiBearingY + (64 / 2)) / 64);
 
-			for (int iy = MAX(-letter_y, 0); letter_y + iy < MIN(letter_y + converted.rows, (unsigned int)surface->h); ++iy)
+			for (int iy = MAX(-letter_y, 0); letter_y + iy < MIN(letter_y + (int)converted.rows, surface->h); ++iy)
 			{
 				if (face->glyph->bitmap.pixel_mode == FT_PIXEL_MODE_LCD)
 				{

src/Main.cpp

@@ -550,6 +550,9 @@ bool SystemTask()
 					case SDL_SCANCODE_F5:
 						gbUseJoystick = false;
 						break;
+
+					default:
+						break;
 				}
 				break;
 			#else