vga: cleanups, prepare for endianness switching

# gpg: Signature made Thu 02 Oct 2014 08:10:49 BST using RSA key ID D3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"

* remotes/kraxel/tags/pull-vga-20141002-1:
  vga: Add endian to vmstate
  vga: Make fb endian a common state variable
  vga: Rename vga_template.h to vga-helpers.h
  vga: Remove some "should be done in BIOS" comments
  cirrus: Remove non-32bpp cursor drawing
  vga: Simplify vga_draw_blank() a bit
  vga: Remove rgb_to_pixel indirection
  vga: Separate LE and BE conversion functions
  vga: Remove remainder of old conversion cruft
  vga: Start cutting out non-32bpp conversion support

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>