Fix PR c++/7612.
	* cplus-dem.c (demangle_signature): Call string_delete.
	Remove extra string_init.
	(demangle_arm_hp_template): Call string_delete instead of
	string_clear.  Add missing string_delete call.
	(demangle_qualified): Add missing string_delete call.
	(do_type): Remove unused variable btype.  Add missing string_delete
	call.  Call string_delete instead of string_clear.
	(demangle_fund_type): Move variable btype inside of the switch
	statement.  Add missing string_delete call.
	(do_arg): Call string_delete instead of string_clear.  Remove extra
	string_init.
	(demangle_nested_args): Free work->previous_argument.

From-SVN: r62852