Make graphite and pthread work with vendor/psd/products/psd_device.mk by using a pa hooks file:

See previous commit for hammerhead.  This is much better than having to use device trees.
Use := and not += in product files.

Signed-off-by: Paul Beeler <pbeeler80@gmail.com>
Move psd strings to vendor/psd (1/2): hammerhead
Add -pthread flag for C and CPP (1/2)