PlatformAndroid: Map back button to Esc key in android.
Fixed sample builds for Android

Default target for Android builds is armeabi-v7a for a while, updated
the samples to build with that.
Merge pull request #1111 from rgngl/androidBackButton

PlatformAndroid: Map back button to Esc key in android.
Merge pull request #1112 from rgngl/samplesAndroidFix

Fixed sample builds for Android