* builtins.c (fold_builtin_fputs): Don't bother converting the
	return type to integer_type_node, as we've already checked that
	the result will be ignored.

	* tree-eh.c (tree_could_trap_p): Add support for -ftrapv such
	that signed addition, subtraction, multiplication, division,
	remainder, negation and absolute value may potentially trap.

	* fold-const.c (fold_ignored_result): New function to strip
	non-side-effecting tree nodes from an expression whose result
	is ignored.
	(fold_convert): Call fold_ignored_result when casting a value
	to VOID_TYPE.
	(omit_one_operand):  Call fold_ignored_result on the "omitted"
	operand when building a COMPOUND_EXPR.
	(pedantic_omit_one_operand): Likewise.
	* tree.h (fold_ignored_result): Prototype here.
	* tree-ssa-ccp.c (ccp_fold_builtin): Call fold_ignored_result
	when we're going to ignore the result.

From-SVN: r84525