Optionally set compiler via CC variable & add -Wno-deprecated-copy to CFLAGS

[jvanns]

I've tried to build this in a g++-10 environment where the g++/gcc 'alternative' links don't exist. To quickly overcome this, allow the CC env var to be set.

Also, modern compilers now issue a warning about the use of the copy assignment operator so add -Wno-deprecated-copy to retain that clean output ;)

Pull request coming ...