build: fix build with vdpau, simplify

Instead of generating vdpau_template.c with a Perl script, just include
the generated file in git. This is ok because it changes very rarely,
and the script is larger than the output it generates.

It also simplify the Makefile, and fixes the build. The problem was that
transitive dependencies do not work with generated files: there is no
dependency information yet when building it the first time. I overlooked
this because I didn't delete the .d files for testing (which contained
the correct dependencies, but only _after_ a first successful build).
command: silence a warning

This is unreachable code, but the compiler doesn't always determine
this. This change shuts up the warning in these cases.