configure: manage libkmod.pc.in and version.py.in via AC_CONFIG_FILES

configure: manage libkmod.pc.in and version.py.in via AC_CONFIG_FILES

Replace the manual sed command, build rules and dist/clean for using
AC_CONFIG_FILES. It does the exact same thing, with an added bonus...

Currently we're missing version.py.in in the EXTRA_DIST. Thus a simple
"touch Makefile" should retrigger the regeneration of version.py. Which
would presumably fail, since the input file isn't in the distribution
tarball.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>