For Travis CI - Install libasound2-dev only when targetting Linux.
Closes #430.
For Travis CI - Upgrade to Android NDK r10 and SDK r23.0.2.
Closes #429.
For Travis CI - For MinGW STATIC build, retry sample build for 3 times.
Each retry should build starts from where it fails, so hopefully it would not hit the memory limit.
Closes #431.
Fix Angelscript binding for TileMapObject2D.