Add Android.bp.

Unfortunately blueprint file doesn't support foreach, so we need 3
blocks of protocol definitions. gensrcs module can't be used until it
allows output file base name manipulation.

Test: "mma -j128" built wayland-protocols for x86/x86_64/arm.
Change-Id: Ifb10a998a0c9d3d5439781e98cb51544bfd35aa7