[LinuxBIOS] State of the buildrom

[Myles Watson]

This is the same patch, updated to use HEAD instead of 539.  Because
of the way linuxbios.inc works, this only gets the true head the first
time, then it just takes the previously built tarball.  So if you
really want the new head you have to remove the tarball.

I also created a new variable LINUXBIOS_SVN_DIR to keep it from
getting v2 and v3 confused with version numbers when you switch back
and forth.

I added an option to use the lgdt patch from the mailing list which
enables compilation on the compilers I have.

I fixed a bug I introduced in the last patch when I added an extra @
to a line in linuxbios.inc

Myles

Signed-off-by: Myles Watson <myles at pel.cs.byu.edu>