runtime: align first persistentalloc chunk as requested

    
    Backport of upstream https://golang.org/cl/163859.
    
    This fixes various failures on 32-bit SPARC.
    
    Patch from Eric Boctazou.
    
    Reviewed-on: https://go-review.googlesource.com/c/163860

From-SVN: r269258

gcc/go/gofrontend/MERGE

-bc036b3a03e089e78b892067e40dbb0e7ecca9e2
+c9581de3804f94c5a74ce14befce5c57368722b9
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/runtime/malloc.go

@@ -1269,7 +1269,7 @@ func persistentalloc1(size, align uintptr, sysStat *uint64) *notInHeap {
 				break
 			}
 		}
-		persistent.off = sys.PtrSize
+		persistent.off = round(sys.PtrSize, align)
 	}
 	p := persistent.base.add(persistent.off)
 	persistent.off += size