add sgabios blob and submodule

The rom was not added together with the sgabios device and is
not installed.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

.gitmodules

@@ -16,3 +16,6 @@
 [submodule "roms/qemu-palcode"]
 	path = roms/qemu-palcode
 	url = git://repo.or.cz/qemu-palcode.git
+[submodule "roms/sgabios"]
+	path = roms/sgabios
+	url = git://git.qemu.org/sgabios.git

Makefile

@@ -253,7 +253,7 @@ ar      de     en-us  fi  fr-be  hr     it  lv  nl         pl  ru     th \
 common  de-ch  es     fo  fr-ca  hu     ja  mk  nl-be      pt  sl     tr
 
 ifdef INSTALL_BLOBS
-BLOBS=bios.bin vgabios.bin vgabios-cirrus.bin \
+BLOBS=bios.bin sgabios.bin vgabios.bin vgabios-cirrus.bin \
 vgabios-stdvga.bin vgabios-vmware.bin vgabios-qxl.bin \
 ppc_rom.bin openbios-sparc32 openbios-sparc64 openbios-ppc \
 pxe-e1000.rom pxe-eepro100.rom pxe-ne2k_pci.rom \

pc-bios/README

@@ -19,6 +19,12 @@
   https://github.com/dgibson/SLOF, and the image currently in qemu is
   built from git tag qemu-slof-20111013.
 
+- sgabios (the Serial Graphics Adapter option ROM) provides a means for
+  legacy x86 software to communicate with an attached serial console as
+  if a video card were attached.  The master sources reside in a subversion
+  repository at http://sgabios.googlecode.com/svn/trunk.  A git mirror is
+  available at git://git.qemu.org/sgabios.git.
+
 - The PXE roms come from the iPXE project. Built with BANNER_TIME 0.
   Sources available at http://ipxe.org.  Vendor:Device ID -> ROM mapping:
 

sgabios @ 23d47494

+Subproject commit 23d474943dcd55d0550a3d20b3d30e9040a4f15b