tcx: Implement hardware acceleration

The S24/TCX framebuffer is a mildly accelerated video card with
blitter, stippler and hardware cursor.

* Solaris and NetBSD 6.x use all the hardware acceleration features
* The Xorg driver (used by Linux) can use the hardware cursor only

This patch implements hardware acceleration in both 8 bit and 24 bit
modes. It is based on the NetBSD driver sources and from tests with
Solaris.

Signed-off-by: Olivier Danet <odanet@caramail.com>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Merge remote-tracking branch 'remotes/mcayland/tags/qemu-sparc-signed' into staging

tcx: Implement hardware acceleration

# gpg: Signature made Tue 23 Sep 2014 22:52:34 BST using RSA key ID AE0F321F
# gpg: Can't check signature: public key not found

* remotes/mcayland/tags/qemu-sparc-signed:
  tcx: Implement hardware acceleration

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