calls.c: refactor special_function_p for use by analyzer (v2)

calls.c: refactor special_function_p for use by analyzer (v2)

This patch refactors some code in special_function_p that checks for
the function being sane to match by name, splitting it out into a new
maybe_special_function_p, and using it it two places in the analyzer.

gcc/analyzer/ChangeLog:
	* analyzer.cc (is_named_call_p): Replace tests for fndecl being
	extern at file scope and having a non-NULL DECL_NAME with a call
	to maybe_special_function_p.
	* function-set.cc (function_set::contains_decl_p): Add call to
	maybe_special_function_p.

gcc/ChangeLog:
	* calls.c (special_function_p): Split out the check for DECL_NAME
	being non-NULL and fndecl being extern at file scope into a
	new maybe_special_function_p and call it.  Drop check for fndecl
	being non-NULL that was after a usage of DECL_NAME (fndecl).
	* tree.h (maybe_special_function_p): New inline function.