frontend: check RIG_SIMULATOR env var for non-debug builds too
Make gstreamer an optional dependency
image-source: Add _get_natural_size() api
shell: strip out most android specific code
updates linux and osx build scripts and starts android build script

This updates the scripts for building linux and osx binaries of the Rig
editor.

This also adds an initial script for building a set of
PREBUILT_SHARED_LIBRARY modules for Android that can be used for
running Rig on an android device.

This also adds an android/project that contains an Android project that
can be used to build the rig-simulator.
fix: Make gstreamer an optional dependency
Guard xlib specific code
fix: updates linux and osx build scripts and starts android build script
Add fmemopen fallback implementation for OSX and Android
android/project use fmemopen fallback