Enhance AIDL to take an explicit id for methods

This adds an annotation to methods in AIDL of the form
"void myMethod() = 3;" to explicitly set the onTransact
id for the method.  Either all methods must have explicitly
annotated id's or none of them should be explicitly annotated.
There is error checking in the AIDL compiler
for duplicate id's and id's outside of the valid range.

Bug: 7353910
Change-Id: I868045e3f112c9a279c573cea368a621116cbf77