[SDL2] function call bottleneck

[daltomi]

DIV-Games-Studio/src/divvideo.c

Lines 590 to 595 in dc8b7e5

	OSDEP_UpdateRect(vga,0,0,vga_an,vga_al);
	if(SDL_MUSTLOCK(vga))
	SDL_UnlockSurface(vga);
	OSDEP_Flip(vga);

The problem is that the function OSDEP_UpdateRect only does internally is call OSDEP_Flip, so hare the function is being called 2 times. See: src/shared/osdep/osd_sdl2.c , branch: master

Maybe in modern computers the speed drop is not noticeable but mine is. Moving the windows or the mouse cursor is noticeable slower.

Proposal: A conditional guard should exist for the SDL2 implementation to only call one.