contrib: avoid cmake rewriting gcc sysroot on Darwin
contrib: gettext: fix android build

We only need autopoint to autoreconf packages
contrib: gettext: avoid spawning extra sub-shells
mmdevice: move volume, mute and device control to dedicated thread

This should allow changing them from within a thread using STA.
(The plugin still cannot be instantiated from such thread though.)

Also fix MTA enter/leave in a few places.