Don't exit a sub via next

If your lib/ contained anything but .pm files you would get a bunch of
perl warnings about next'ing out of the sub instead of returning.
Allow for an html/ directory

RT doesn't have one (since the 3.8 days) but external extensions use
html not share/html.
Check for the existence of items before tagging

When running this script outside of RT, you often won't have a
devel/tools or a Makefile.in
Merge branch '4.0/more-flexible-license_tag' into 4.0-trunk