[mythtv-cmyth] No need to store file control connection

It is ref counted: libcmyth/file.c line 137

To get it we have function: cmyth_file_control()
[cmyth] Handle UTC timestamp

Changes allow to handle UTC times. Since Myth protocol 0.26 commands can return time values using
format ISO8601 and containing the zone flag 'Z'. Until now no help to handle them. Here i add tools
to process them.

I banned the conversion from UTC timestamp to 'time_t' type. Once timestamp created as UTC time, it
can be formatted as string or other for processing only.

Add new attribut 'timestamp_isutc' equal 1 when timestamp contains UTC time. UTC timestamp can be
create by two ways:
- First using function cmyth_timestamp_utc_from_unixtime().
- Second using function cmyth_timestamp_from_string(). Here if the string is formatted using standard
ISO8601 and constains 'Z' after seconds the function flags 'timestamp_isutc'.

Update 'to_string()' and 'to_display()' functions to consider timestamp_isutc.
Prohibit conversion in all functions using 'mktime()' by returning NULL or (time_t) -1.
Add new function 'cmyth_timestamp_to_utc()' to convert local timestamp to UTC timestamp.
Add new function 'cmyth_timestamp_isutc()' to retreive the zone type of timestamp: 1 = UTC , 0 = local
[cmyth] LiveTV chain info: returning last program / file handle by recorder
[mythtv-cmyth] Review recordings UID and all about recording events

Many problems with it and myth protocol changes. So to resolve for long term
i rationalized the UID. Now it is formatted like "1002 2013-08-23T14:42:00Z"
and contains myth channel id and recstartts as UTC time. Regardless myth
version our UID use UTC time only.
Depending of protocol command, backend messages could be filled with time
values containing Unix time or string using ISO8601 standard. The string can
contains UTC or local time. To process recording events from backend we must
match backend message with recording UIDs.
Merge branch 'cmyth_improvement' into local

Conflicts:
	addons/pvr.mythtv.cmyth/src/cppmyth/MythProgramInfo.cpp