Change the way video graphics adapter is selected

Instead of having (current)three command line switches -std-vga,
-cirrusvga and -vmwarevga, provide one -vga switch which takes
an argument, so that:
qemu -std-vga   becomes qemu -vga std
qemu -cirrusvga becomes qemu -vga cirrus
qemu -vmwarevga becomes qemu -vga vmware

Update documentation accordingly.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5335 c046a42c-6fe2-441c-8c8c-71466251a162

qemu-doc.texi

@@ -955,11 +955,24 @@ images.
 @item -L path
 Set the directory for the BIOS, VGA BIOS and keymaps.
 
-@item -std-vga
-Simulate a standard VGA card with Bochs VBE extensions (default is
-Cirrus Logic GD5446 PCI VGA). If your guest OS supports the VESA 2.0
-VBE extensions (e.g. Windows XP) and if you want to use high
-resolution modes (>= 1280x1024x16) then you should use this option.
+@item -vga @var{type}
+Select type of VGA card to emulate. Valid values for @var{type} are
+@table @code
+@item cirrus
+Cirrus Logic GD5446 Video card. All Windows versions starting from
+Windows 95 should recognize and use this graphic card. For optimal
+performances, use 16 bit color depth in the guest and the host OS.
+(This one is the default)
+@item std
+Standard VGA card with Bochs VBE extensions.  If your guest OS
+supports the VESA 2.0 VBE extensions (e.g. Windows XP) and if you want
+to use high resolution modes (>= 1280x1024x16) then you should use
+this option.
+@item vmware
+VMWare SVGA-II compatible adapter. Use it if you have sufficiently
+recent XFree86/XOrg server or Windows guest with a driver for this
+card.
+@end table
 
 @item -no-acpi
 Disable ACPI (Advanced Configuration and Power Interface) support. Use