docs-rst: improve typedef parser

Improve the parser to handle typedefs like:

	typedef bool v4l2_check_dv_timings_fnc(const struct v4l2_dv_timings *t, void *handle);

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>