fix keyCopy()'s ignorance of flags

clear flags as they lead to failed keySetName() with
source/dest->flags=KEY_FLAG_RO_NAME

maybe introduced around adding KEY_FLAG_RO_NAME in #6f07e18f
No idea, if the project builds against a non gcc tool chain.
set (C_STD "--std=gnu99")
Above cmake command suggests, it would be fine to skip "--std=c++11" etc.