bugs: Add a bug about tartan --help
scripts: Improve escaping arguments when passing through to clang

We should escape the arguments when called with --analyze, but not
otherwise, as that’s when Clang is building multiple command lines for
analysis and compilation, and needs to be able to differentiate plugin
arguments.

Pass the plugin arguments with -Xclang and -Xanalyzer in that case.
gerror: Remove unreachable code

Whoops, left some experimental code in place.
gerror: Fix crash when running on non-GLib code

If the GError checker was run on non-GLib code, the assertion about
having the typedef for the GError structure would fail and cause Clang
to abort. This was commonly being triggered when running the checker in
a configure script.

Fix that by gracefully and rapidly bailing out of the GError checker if
glib.h has not been included in this AST context.