stapdyn & staprun: Use the top-level git_version.h

stapdyn & staprun: Use the top-level git_version.h

Yo dawg, I herd you like Makefile recursion, so I put some recursion in
your recursion so you can version while you version.

Less duplication + more recursion == win?  Another option is to flatten
stapdyn and staprun Makefiles altogether into the root Makefile, but for
now, this is less invasive.

Changing the includes to ../git_version.h is not strictly necessary,
since we also have "-I..", but this way developers won't get burned by
old git_version.h files sitting in staprun/ or stapdyn/.