Fixes a major regression which allowed OpenGL
compositing to be used with software rasterizer, which
either did not work or crashed directly.
Cherry-picked from cf2f572 in branch KDE/4.7.
Adding a new method to retrieve whether the OpenGL implementation
uses any kind of software emulation and no software emulation can
provide GLSL support, even if it claims so.
Thanks to Maurel for testing again and again proposed patches.
BUG: 271166
Second part of cleaning up the lib directory: the effects library
now lives in libkwineffects/ directory.
For existing effects nothing changes as the install path is unchanged.
The change obsoletes the lib/ directory.
As glplatform.h has not yet been exported I dared to export it and
adjust the places where it is used.
CCMAIL: kwin@kde.org
