Add --with-pkgversion.
Allows distributors to identify their builds without needing to hack the
sources.

Signed-off-by: Paul Brook <paul@codesourcery.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7036 c046a42c-6fe2-441c-8c8c-71466251a162
