re PR c++/48008 (libstdc++-v3/testsuite/20_util/function/43397.cc fails to assemble with -fabi-version=5)

	PR c++/48008
	* mangle.c (write_type): Strip cv-quals from FUNCTION_TYPE here.
	(write_CV_qualifiers_for_type): Not here.

From-SVN: r170752