ada: Static intrinsic functions are a core language extension.

ada: Static intrinsic functions are a core language extension.

GNAT-defined Ada extensions are divided into two categories: those that are
enabled by either -gnatX or -gnatX0 and those which require -gnatX0.
Move static intrinsic functions from the second category into the first.

gcc/ada/

	* doc/gnat_rm/implementation_defined_pragmas.rst: Add the standard
	'... "On" enables this extension.' sentence to the description of
	static intrinsic functions.
	* sem_ch13.adb
	(Analyze_Aspect_Spec): In the call to Error_Msg_GNAT_Extension for
	a Static aspect specification for an intrinsic function, specify
	Is_Core_Extension => True.
	* sem_eval.adb
	(Eval_Intrinsic_Call): Test Core_Extensions_Allowed instead of
	testing All_Extensions_Allowed.
	* gnat_rm.texi: Regenerate.