[mythtv] Shm detection + frame decimation environment variable

[Chris Pinkham]

I've added this functionality but coded it a little different.  It's in
current CVS if you want to give it a shot.

The XShmQueryExtension() function will report true if you are displaying
remotely to a server that supports XShm even though you can't use XShm
remotely.  My mod checks the display variable to see if the display is
local or remote and will only call XShmQueryExtension() if it's a local
display.  If remote display then use_shm stays at it's default of 0.

I also added in a little bit of code to the Show() function to calculate
how many frames are processed in the first 4 seconds.  If it determines the
fps is too slow, it will print out a message and will skip frames similar
to your mod in order to keep the audio and video in sync.  

> Another little patch.  The first bit sets the default value of 
> use_shm to whether or not the SHM extension is found 
> (false for cygwin-XF86).
> 
> The second part reads the SKIP environment variable and
> displays 1 out of SKIP frames.  On my 100MBit lan, I can
> do SKIP=3 mythfrontend, and the video will be ok'ish 
> (640x480) using X to do the video rendering.
> 
> Basically this lets me develop MythTV from a remote X server
> without hassle.
> 
> FWIW,
> -Thor Johnson

Chris

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** Chris Pinkham                  Linux v2.2.18, Sane v1.0.4, Cajun v3.0-8 **
** cpinkham at bc2va.org                          http://www.bc2va.org/chris/ **
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