Add aidl file support to java builds

Add support for aidl files listed in srcs for java builds, and
an aidl_preprocess module type for framework and sdk aidls.

Change-Id: I3aa537f4483822e5b534c74d0b35f13a938f8947
diff --git a/root.bp b/root.bp
index 18e734f..fbd0be2 100644
--- a/root.bp
+++ b/root.bp
@@ -10,4 +10,5 @@
     "prebuilts/ndk",
     "prebuilts/sdk",
     "system/core/*",
+    "frameworks/base/tools/aidl",
 ]