Force RoboVM to keep all Scene2d UI classes

Because skins are loaded by reflection, some classes may not be
linked in the RoboVM binary (RoboVM only includes classes explicitly
used). This forces them to be linked.
Test shader: dont assume varying is removed
Merge pull request #739 from xoppa/3dapi

Test shader: dont assume varying is removed
Fix other test shaders
Merge pull request #740 from xoppa/3dapi

Fix other test shaders
Fix bug in calculation of ppcY (RoboVM)

Manual merge of PR #741
fixed FileHandle#read
Merge branch 'master' of https://github.com/libgdx/libgdx
and reverted
Increment set methods for numeric arrays.
Merge branch 'origin/master'
RoboVM backend didn't create a depth buffer
fixed buffer format on robovm backend
added multitouch to robovm todods
more changes to robovm config
Javadocs.
Merge branch 'origin/master'