middle-end/110200 - genmatch force-leaf and convert interaction

middle-end/110200 - genmatch force-leaf and convert interaction

The following fixes code GENERIC generation for (convert! ...)
which currently generates

  if (TREE_TYPE (_o1[0]) != type)
    _r1 = fold_build1_loc (loc, NOP_EXPR, type, _o1[0]);
    if (EXPR_P (_r1))
      goto next_after_fail867;
  else
    _r1 = _o1[0];

where obviously braces are missing.

	PR middle-end/110200
	* genmatch.cc (expr::gen_transform): Put braces around
	the if arm for the (convert ...) short-cut.