AIDL previously supported "rpc" and "flatten" types, which are not used
anywhere in the Android tree. This patch removes them, which significantly cuts
down code and complexity.
Bug: 23517584
Test: Rebuilt AOSP tree against new version
Change-Id: I6cf38d43c1ce109ffca987cc14520945aa22431f
Signed-off-by: Casey Dahlin <sadmac@google.com>