Avoid "'dc' may be uninitialized" warning.

	libiberty/
	* cp-demangle.c (d_demangle_callback): Put an abort call in place,
	to help the compiler.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@207200 138bc75d-0d04-0410-961f-82ee72b054a4