tweak type_new to get a nice natural number for the new size

theories/typing/examples/lazy_lft.v

theories/typing/lft_contexts.v

theories/typing/lib/cell.v

theories/typing/lib/mutex/mutex.v

theories/typing/lib/mutex/mutexguard.v

theories/typing/lib/rc/rc.v

theories/typing/lib/rc/weak.v

theories/typing/lib/refcell/refcell_code.v

theories/typing/lib/rwlock/rwlock_code.v

theories/typing/own.v