Add dependency generation to Aapt for R.java

Add dependency generation to Aapt for R.java

Make Aapt generate a dependency file in the location specified
by RClassDir for R.java if the --generate-dependencies flag is set.
This dependency file is then read by the ant exec loop task
to see whether to recreate R.java.

Change-Id: I7152dac86b6ea0e448ef65e3a95694afe233c789