compiler: Disallow use of unary ^ on booleans.

Fixes golang/go#11529.
    
    Reviewed-on: https://go-review.googlesource.com/13790

From-SVN: r227201

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-f97d579fa8431af5cfde9b0a48604caabfd09377
+d5e6af4e6dd456075a1ec1c03d0dc41cbea5eb36
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/expressions.cc

@@ -3943,9 +3943,8 @@ Unary_expression::do_check_types(Gogo*)
       break;
 
     case OPERATOR_XOR:
-      if (type->integer_type() == NULL
-	  && !type->is_boolean_type())
-	this->report_error(_("expected integer or boolean type"));
+      if (type->integer_type() == NULL)
+	this->report_error(_("expected integer"));
       break;
 
     case OPERATOR_AND: