Added release branch for 1.8.x

svn path=/branches/releases/1.8.x/; revision=9558
cherry-pick r9635

svn path=/branches/releases/1.8.x/; revision=9640
Fix XInput error, #489

svn path=/branches/releases/1.8.x/; revision=9651
1.8.x branch: cherry-pick 9648 from trunk.

svn path=/branches/releases/1.8.x/; revision=9653
1.8.x branch: cherry-pick 9629, 9630 from trunk.

svn path=/branches/releases/1.8.x/; revision=9654
1.8.x branch: cherry-pick 9637, 9636 from trunk.

svn path=/branches/releases/1.8.x/; revision=9655
1.8.x branch: Updated NEWS.

svn path=/branches/releases/1.8.x/; revision=9656
releases/1.8.x branch: Updated version number.

svn path=/branches/releases/1.8.x/; revision=9677
releases/1.8.x branch: Cherry-picked libav 0.10.0 support.

svn path=/branches/releases/1.8.x/; revision=9678
WIP: Some #ifdef towards rpi again
Fixed issue #496
Updated NEWS
Merge branch 'master' into fix/egl
Fixed tests for non-gles build.
Fixed linking on Ubuntu 14.04/NVidia
Merge branch 'fix/egl' of github:libavg/libavg into fix/egl
Fix screenshot function under GLES/EGl

Fixes most tests
Skip MultiWindow test when using GLES/EGL
Free Colormap
Fixed audio decoding (#500)