[cmyth] Add function cmyth_mysql_get_recording_seek_offset (Assistance from janbar)

Function returns offset for mark and type from position map of recording (table recordedseek).
[mythtv-cmyth] EDL: Use position/duration/seeking since mythtv 0.27

Since MythTV 0.27 backend provide accurate position/duration/seeking with
non-constant frame rates. Note that to get the benefit of these changes for
preexisting recordings, it may be necessary to run "mythcommflag --rebuild"
on affected recordings.
Depending of backend database version, we check if new type of mark (33)
exists else fallback using old method based on framerate.
[mythtv-cmyth] When EDL start_mark is zero, assume 0ms offset. Skip DB seek

mythcommflag does not always rebuild the recordedseek table starting from 0,
which can put the start of a break that is at the beginning of a recording
off by a half-second or more.

Also add in a check to see if a DB seek for end_mark offsets failed. If they
failed, fallback to the static framerate guess.
[cmyth] For protocol >= 77, do not send trailing blank parameter with SET_BOOKMARK

This uselss parameter was removed in MythTV 0.27, protocol 77.

Reference:
http://code.mythtv.org/trac/ticket/11104
http://code.mythtv.org/trac/changeset/a8722faea68e8f7d2bb12f31bf78d6bc272dbdde/mythtv
Merge branch 'set_bookmark_myth_77' of https://github.com/nerddtvg/xbmc-pvr-addons into local