Notice for systemtap.git/master users

[Josh Stone]

For everyone building and installing from git master lately, beware of
"dirty" installation directories.  As described in PR14179 and PR14180,
I've been moving files around in runtime/ and tapset/.  But if you've
just been continuously running "make install" on top of old builds, you
may end up with some outdated files left in a bad place.

Just make sure to clean up your installation target first, and it should
be fine.

Josh