[mythtv] Raspberry Pi dev branch

[Lawrence Rust]

Hi all,

I would like to push a number of patches to support the Raspberry Pi.
However, some of the patches affect OpenGL, in particular the GUI and
video rendering, which could affect many other systems so I'd like to be
cautious.

I have created a devel/lvr/rpi branch with the proposed patches (45 in
total).  I would appreciate any comments, suggestions or bug reports
before I finally commit them to the master branch.

The patches are grouped into and affect these areas:

- configure.  To support cross compilation
- UPnP.  To support Qt builds without SSL
- UI.  To support the Qt EGLFS platform (OpenGLES)
- ALSA.  To work around some differences on the RPi
- TV.  Fix some problems with the softblend OSD.

The UI group includes some significant changes to the OpenGL code so I
would appreciate any feedback on compatibility or bugs.  Notably I have
tested only on Intel systems with integrated graphics as I don't have
any current Nvidia or Radeon graphics adapters.  The OpenGL changes will
affect the Android platform the most, so anyone who can test this area
would be appreciated.

The patches provide the following new features:

- An OpenMAX video decoder (h/w accelerated).  NB a license file is
required for MPEG2/4 decoding on the RPi.
- An OpenMAX video renderer with an EGL based OSD.
- An OpenGLES 2.0 based video renderer.
- GUI rendering by Qt (EGLFS and X platforms) or by OpenGLES.  The
OpenGLES GUI is still buggy (Qt 5.4.0) so is only enabled if the GUI is
specifically set to OpenGL.
- An OpenMAX audio renderer with support for EAC3 & DTS pass through.
- An OpenMAX audio decoder.  This is currently incomplete as the RPi
OpenMAX implementation doesn't support common MP1/2/3 or AC3 formats due
to licensing restrictions.

OpenMAX is also available for Windows so it may be feasible to use these
patches on that platform too.

-- Lawrence Rust