MSC: short far _setvideomode( short mode )

	- prototype in graph.h

	- sets video mode specified
	- mode=	_DEFAULTMODE	hardware default
		_MAXCOLORMODE	graphics mode with most colors
		_MAXRESMODE	graphics mode with highest resolution
		_TEXTBW40	 40x25	  16 color  CGA/Text
		_TEXTC40	 40x25	  16 color  CGA/Text
		_TEXTBW80	 80x25	  16 shades CGA/Text
		_TEXTC80	 80x25	  16 color  CGA/Text
		_MRES4COLOR	320x200    4 color  CGA/Graphics
		_MRESNOCOLOR	320x200    4 color  CGA/Graphics
		_HRESBW		640x200    2 color  CGA/Graphics
		_TEXTMONO	 80x25	      mono  MDA/Text
		_MRES16COLOR	320x200   16 color  EGA/Graphics
		_HRES16COLOR	640x200   16 color  EGA/Graphics
		_ERESNOCOLOR	640x350    1 color  EGA/Text
		_ERESCOLOR	640x350   64 color  EGA/Graphics
		_VRES2COLOR	640x480    2 color  VGA/Graphics
		_VRES16COLOR	640x480   16 color  VGA/Graphics
		_MRES256COLOR	320x200  256 color  VGA/Graphics
		_ORESCOLOR	640x400   16 color  CGA/Graphics/Olivetti
		_HERCMONO	720x348    2 color  HGC/Graphics/Hercules

	- returns non-zero on success; zero on error