Currently the versions are set in the header, and then sed is used to
extract them, so that autotools can use them elsewhere.

This is odd. Autotools is perfectly capable of configuring the header
with the versions, and then they don't need to be extracted from the
the header. This is cleaner and more obvious.

Tested with make distcheck.

v2: - Split tiny -> patch change
    - Drop temporary variables
    - change XA_VERSION_* -> XA_*
v3: - Finish splitting the tiny -> patch change

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Emil Velikov <emli.velikov@collabora.com>
Reviewed-by: Matt Turner <mattst88@gmail.com> (v2)