Add a missing include directory in the android makefiles
Remove unused proguard config files
Ignore files generated while building the android projects
Remove unnecessary commented out code in the android makefiles

Comments isn't a place to store code snippets that might (or
might not) be useful later.
Merge pull request #315 from mstorsjo/android-cleanup

Minor cleanup of the android build files
Merge remote-tracking branch 'upstream/master' into travis.android