Use-after-free through `init_using_cdict` and `init_using_ddict`

CCtx::initusingcdict and DCtx::initusingddict experimental feature, deprecated took the dictionary as &CDict and &DDict with only 'b: 'a, so the dictionary itself could be dropped while the context still pointed at it. The same mistake in other constructors was fixed earlier . The flaw was...