* upstart/control.c: Rename to upstart/message.c
* upstart/control.h: Rename to upstart/message.h
* upstart/tests/test_control.c: Rename to upstart/tests/test_message.c
* upstart/libupstart.h: Update includes.
* upstart/wire.c: Include message.h
* upstart/wire.h: Update includes.
* upstart/tests/test_wire.c: Update includes.
* upstart/errors.h: Rename UPSTART_INVALID_MESSAGE to
UPSTART_MESSAGE_INVALID so that it's prefixed.
* upstart/Makefile.am (libupstart_la_SOURCES) 
(upstartinclude_HEADERS, TESTS): Update filenames.