Android: Add working defaults to configure

My current configure line for Android builds is:

configure -opensource -opengl es2 -developer-build -xplatform android-g++ -no-largefile -pch -nomake examples -nomake tests -no-qpa-platform-guard -confirm-license

OpenGL ES2 should be detectable, no-largefile should be a default of some kind, -no-qpa-platform-guard should be a default, etc.

In short: We should get the required parameters for Android down to what's common on other platforms. Namely just -xplatform.