This avoids some warnings when building with -fno-rtti because the
function parameters are only used when RTTI is enabled.

libstdc++-v3/ChangeLog:

	* include/bits/shared_ptr_base.h (__shared_ptr::_M_get_deleter):
	Add unused attribute to parameter.
	* src/c++11/shared_ptr.cc (_Sp_make_shared_tag::_S_eq):
	Likewise.

Tested powerpc64le-linux. Committed to trunk.