Organize barrier makefiles
Introduce a custom audio-hal

The QCOM audio hal introduced in Android 4.3 has several
incompatabilities with our device:
1) TX DEVICE should be HANDSET when headphones are plugged in
during calls instead of DMIC.
2) ADBD IDs are now hard coded into the HAL making it difficult
to change the IDs without introducing ifdefs or affecting other
devices

This HAL is a copy of hardware/qcom/audio/hal.
A device tree must set TARGET_QCOM_AUDIO_VARIANT to "custom" to
activate this build and overwrite the qcom tree variant