compiler: include "go-system.h" in escape.cc

    
    Patch from Rainer Orth.
    
    Reviewed-on: https://go-review.googlesource.com/25466

From-SVN: r239140

gcc/go/gofrontend/MERGE

-4ba387176e8a826dd5dd6cad4caa2f93434d0b14
+ca5b64137f013e3104fd74ee7d07ba556a501187
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/escape.cc

@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+#include "go-system.h"
+
 #include <limits>
 #include <stack>
 #include <sstream>