Add typesafe_cb macro from CCAN
Add typesafe_cb macro from CCAN

refu-lang/rfbase,refu-lang/rfbase,LefterisJP/refuclib,LefterisJP/refuclib,LefterisJP/refuclib,refu-lang/rfbase,refu-lang/rfbase,refu-lang/rfbase,LefterisJP/refuclib