ada: Incorrect warning redundant parens on in

ada: Incorrect warning redundant parens on in

This patch fixes a bug where GNAT gives a warning
about redundant parentheses on expressions like "(X in S) = B".
In fact, the parentheses are required in this case.

The bug is caused by constant-folding the expression into
an expression that does not require parentheses, but in
a way that retains the parentheses. The fix is to look
at Original_Node.

gcc/ada/ChangeLog:

	* style.adb (Check_Xtra_Parens_Precedence):
	Give warning based on Original_Node.