Support java annotation proccessors

The codebase is growing more uses of annotation processors,
through a mixture of LOCAL_ADDITIONAL_DEPENDENCIES and
LOCAL_JACK_FLAGS.  Add LOCAL_ANNOTATION_PROCESSORS and handle
the rest in the build system.

For now we also need LOCAL_ANNOTATION_PROCESSOR_CLASSES to
work around bad behavior in grok (b/25860419).

Test: m -j java
Change-Id: I465b021e65d25ed3ea517333a82ec4ebd63fc038
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 3619106..a4751fd 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -12,6 +12,8 @@
 LOCAL_ADDITIONAL_JAVA_DIR:=
 LOCAL_AIDL_INCLUDES:=
 LOCAL_ALLOW_UNDEFINED_SYMBOLS:=
+LOCAL_ANNOTATION_PROCESSORS:=
+LOCAL_ANNOTATION_PROCESSOR_CLASSES:=
 LOCAL_APK_LIBRARIES:=
 LOCAL_ARM_MODE:=
 LOCAL_ASFLAGS:=