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
diff --git a/tools/aapt/Main.h b/tools/aapt/Main.h
index 3ba4f39..1df1144 100644
--- a/tools/aapt/Main.h
+++ b/tools/aapt/Main.h
@@ -46,4 +46,5 @@
 String8 getAttribute(const ResXMLTree& tree, const char* ns,
                             const char* attr, String8* outError);
 
+status_t writeDependencyPreReqs(Bundle* bundle, const sp<AaptAssets>& assets, FILE* fp);
 #endif // __MAIN_H