BoardConfig.mk: update CPU variant selection settings for Android 4.3

Change-Id: I24387c43ee18b6ce4249fd66ec311b33dc27f7d0
Use the Android 4.3 unified fstab

Many thanks to drmarble for doing the work to figure this out.

Change-Id: I6d76e94ff8d2c34ea232d7299364feb880266cba
Update build fingerprint to match takju 4.3

Change-Id: Ibd0e465c203df4a8a6ed9d737a5b1c6becb1938f
Disable GPU producer -> CPU consumer in the display stack (unsupported by h/w)

Change-Id: Ie1873456e755a745dbdffee941ece62eaacbca27
Disable Bluetooth stack features not supported by hardware

Change-Id: I981449709f0db63a415a140ed48c893c5ddadae6
Provide libskia_legacy for compatibility with browser saved pages from Android 4.2 and earlier

Change-Id: I5d656776e72de29ecde76311cc17fa20b7b73f89
libgui: don't use EGL_KHR_fence_sync

The EGL implementation for OMAP3/SGX530 has this extension, but
testing shows that it causes stuttering in the UI.

Change-Id: If750df1bc4730e5c27767930af9da89630f0ff1e
proprietary-files.txt: remove unneeded powervr.ini

We inherited this from somewhere a long time ago.  Strictly, it's been
unneeded for a while now, but we kept it because it was needed for
working hwcomposer.  Now that the kernel's been fixed to eliminate the
need for that workaround, we can just get rid of it entirely.

Change-Id: I38525e31cc05182ead7fedd4de6987912e1f5856