ada: Fix crash with -gnatdJ and -gnatyz

This patch makes it so -gnatyz style checks reports specify a node
ID. That is required since those checks are sometimes made during
semantic analysis of short-circuit operators, where the Current_Node
mechanism that -gnatdJ uses is not operational.

Check_Xtra_Parens_Precedence is moved from Styleg to Style to make
this possible.

gcc/ada/

	* styleg.ads (Check_Xtra_Parens_Precedence): Moved ...
	* style.ads (Check_Xtra_Parens_Precedence): ... here. Also
	replace corresponding renaming.
	* styleg.adb (Check_Xtra_Parens_Precedence): Moved ...
	* style.adb (Check_Xtra_Parens_Precedence): here. Also use
	Errout.Error_Msg and pass it a node parameter.