* c-typeck.c (default_function_array_conversion,
	build_function_call): Allow for CONVERT_EXPR as well as NOP_EXPR.
	(build_conditional_expr): Apply integer_zerop to orig_op1 and
	orig_op2.  Don't check them for NOP_EXPR.
	(build_c_cast, convert_for_assignment): Don't check for NOP_EXPR
	around integer zero.

testsuite:
	* gcc.dg/c90-const-expr-4.c, gcc.dg/c99-const-expr-4.c: New tests.

From-SVN: r107990