pulseaudio-modules-droid: audio for hybris adaptations

Add 2 packages:

1. pulsecore-private-headers is needed to "export" unexported private headers from pulseaudio. It is needed to build pulseaudio-modules-droid package.

2. pulseaudio-modules-droid package itself.

Note that pulsecore-private is only needed to build pulseaudio-modules-droid, not required to run them. Read commits descriptions for more information.

Checklist:

• make it compile
• build against multiple android headers variations
• check that it works
• provide default pulseaudio configs for new modules
• better naming for pulsecore-private? pulsecore-private-headers !