Remove stray tab
Include grp.h for setgroups(2)

setgroups(2) in Ubuntu 12.04 (the platform on which the Travis CI
builds run) needs grp.h, so include that to fix the build.
Avoid using strcasestr(3)

The strcasestr(3) function is not present under Ubuntu 12.04 unless
_GNU_SOURCE is defined and I'm not sure I want to go into the route
of defining that.  Just workaround the lack of it by looking for
the two "skip" and "SKIP" strings independently (ignoring any other
possible capitalization).
Add missing newline to kyua_error_fprintf
Cope with the lack of gdb

Mark the stacktrace integration test as skipped if the debugger cannot
be found.  Also, install gdb in the Travis CI environment to get this
to run.
Fix various build problems found in Ubuntu 12.04
Fix paths to various uninstalled files

This lets some additional tests pass before Kyua has ever been installed.
Also fix a typo.