libgo patch committed: Uncomment check for gchelper on g0 stack

[Ian Lance Taylor]

This libgo patch uncomments a check.  Now that systemstack changes to
the g0 stack, the check passes.  Bootstrapped and ran Go testsuite on
x86_64-pc-linux-gnu.  Committed to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 249577)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-c5aa42107d116c9121de447d214297c88dd9f5fa
+385efb8947af70b8425c833a1ab68ba5f357dfae
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: libgo/go/runtime/mgc.go
===================================================================
--- libgo/go/runtime/mgc.go     (revision 249565)
+++ libgo/go/runtime/mgc.go     (working copy)
@@ -1923,10 +1923,9 @@ func gchelperstart() {
        if _g_.m.helpgc < 0 || _g_.m.helpgc >= _MaxGcproc {
                throw("gchelperstart: bad m->helpgc")
        }
-       // For gccgo we run gchelper on the normal g stack.
-       // if _g_ != _g_.m.g0 {
-       //      throw("gchelper not running on g0 stack")
-       // }
+       if _g_ != _g_.m.g0 {
+               throw("gchelper not running on g0 stack")
+       }
 }
 
 // itoaDiv formats val/(10**dec) into buf.