xmltv: add a parser for XMLTV EPG data files
This parser handles XMLTV format files as specified at:
The way the parser was written, once a file is added to
the parser, it keeps monitoring it for file changes.
When a file change is detected, it will reload the file and
parse it, adding entries to the EPG guide.
Signed-off-by: Mauro Carvalho Chehab <email@example.com>