Move custom buffer size handling out of the settings dialog

BufferSize settings in the config files will be ignored as long as
the checkbox is unchecked (UseBufferSize is unset or 0), to make
the contents of the settings dialog reflect actual encoder behavior
Game capture: Update for D3D9 6.3.9600.17085

Latest D3D9 performance patches because microsoft recompiled D3D9 once
again.  Why oh why do they artificially limit D3D9.
Game capture:  make minor GL imrovements

There's no need to create a dummy context for GL -- always use the
game's context.  The dummy context is completely pointless for GL.
Reset stream size if cancelling out of capture
Update version to 0.623b
Revert bad commit e04b481 for further testing
Make failing to open or read a shader file a CrashError