From time to time it's handy to jump directly to a function prototype in
a header. However, generating tags for headers is disabled by default in
ctags, let's enable it by using --c-kinds=+p.
Signed-off-by: NErik Skultety <eskultet@redhat.com>

The .ctags file specifies default options for ctags so that it does not
ignore libvirt.h.in and ignores uninteresting files. As a result, you
can just run "ctags" and navigating to a public API won't get you to a
useless entry in api.html.