Move iproto to box, where it belongs.

src/CMakeLists.txt

src/box/CMakeLists.txt

src/box/box.cc

src/box/iproto.cc

src/box/iproto.h

src/box/iproto_constants.cc

src/box/iproto_constants.h

src/box/iproto_port.cc

src/box/iproto_port.h

src/box/recovery.cc

src/box/recovery.h