Without --with-all-libs (as documented in doc/how-to-build.txt), at least
the "nogui" GUI does not work anymore -- the default for headless
experiments.

(Note the UNDEFINED->UNDEF enum rename; this was necessary due to a vga.h
include side-effect in bochs/gui/svga.cc.)

Change-Id: I1bc3208e905783505a35bbc48ff29f00eef599d6