* upstart/wire.c (upstart_write_int, upstart_write_unsigned) 
(upstart_write_string, upstart_write_header, upstart_write_packv) 
(upstart_write_pack): Rename to *_push_*
(upstart_read_int, upstart_read_unsigned, upstart_read_string) 
(upstart_read_header, upstart_read_packv, upstart_read_pack): Rename
to *_pop_*.
All of the above modified to modify an NihIoMessage structure,
instead of trying to carry around buffers ourself.
* upstart/wire.h: Update to match above.
* upstart/tests/test_wire.c: Update all tests to match the above
changes.