libgo patch committed: clear isSystemGoroutine in goexit

[Ian Lance Taylor]

This patch to libgo clears the isSystemGoroutine field of the g
structure when the goroutine exits.  Otherwise it may be set when the
g structure is reused via gfput/gfget.  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 249138)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-908fc7e46ebe36658ed86b65a3d165fccb2e8576
+3b44ad058abda0d1b0b6c928987270da50ab7431
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: libgo/go/runtime/proc.go
===================================================================
--- libgo/go/runtime/proc.go    (revision 249138)
+++ libgo/go/runtime/proc.go    (working copy)
@@ -2251,6 +2251,7 @@ func goexit0(gp *g) {
        casgstatus(gp, _Grunning, _Gdead)
        if isSystemGoroutine(gp) {
                atomic.Xadd(&sched.ngsys, -1)
+               gp.isSystemGoroutine = false
        }
        gp.m = nil
        gp.lockedm = nil