* fold-const.c (fold_binary_loc): Move bool_var != 0 -> bool_var
and bool_var == 1 -> bool_var simplifications ...
* match.pd: ... to patterns here. Factor out negate_expr_p
cases from the A - B -> A + (-B) patterns as negate_expr_p
predicate and add a -(A + B) -> (-B) - A pattern.