c++: start_preparsed_function tweak

c++: start_preparsed_function tweak

In review of the deducing 'this' patch, it came up that the logic in
start_preparsed_function around the ctype variable was convoluted, being
set for non-static member functions and friends, but not for static member
functions.  Let's set it for any member function, and not rely on it to
decide whether to set up 'this'.

gcc/cp/ChangeLog:

	* decl.cc (start_preparsed_function): Clarify ctype logic.