main/dispatch.c is a glapi source file. It is part of GLAPI_SOURCES in
sources.mak and part of glapi_sources in SConscript. This commit moves
it to glapi/ and renames it to glapi_dispatch.c.
Added the make script version.mk to print the various version numbers
from configs/default. This is used to substitute the version in autoconf
rather than duplicating it in both places.
Just like configs/default, the version number in configure.ac needs to
be bumped for releases. Maybe later we can figure out how to scrape the
version from configs/default into configure.ac.