We failed to call Adjust_Condition for the condition expression of an
if_expression, so non-standard booleans were expanded like standard
booleans, disregarding representation clauses. Fixed.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* exp_ch4.adb (Expand_N_If_Expression): Call Adjust_Condition to
	handle non-standard booleans.