Fix global operator delete definition for C++14 in gc_cpp

Fix global operator delete definition for C++14 in gc_cpp

Issue #195 (bdwgc).

Sized variants of global operator delete should be defined along with
the non-sized ones.  Otherwise compiler might invoke the one from the
standard library (as observed in e.g. Cygwin) leading to a crash.

* gc_cpp.cc [!_MSC_VER && __cplusplus>201103L] (operator delete):
Define sized variant (the size argument is ignored for now).
* gc_cpp.cc [!_MSC_VER && __cplusplus>201103L && GC_OPERATOR_NEW_ARRAY
&& !CPPCHECK] (operator delete[]): Likewise.