runtime, cmd/internal/ld: rename themoduledata to firstmoduledata

'themoduledata' doesn't really make sense now we support multiple moduledata
objects.

Change-Id: I8263045d8f62a42cb523502b37289b0fba054f62
Reviewed-on: https://go-review.googlesource.com/8521
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 130866e..72a10d1 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -322,7 +322,7 @@
 			// So adjust it upward a little bit ourselves: 1/4 MB to get
 			// away from the running binary image and then round up
 			// to a MB boundary.
-			p = round(themoduledata.end+(1<<18), 1<<20)
+			p = round(firstmoduledata.end+(1<<18), 1<<20)
 			pSize = bitmapSize + spansSize + arenaSize + _PageSize
 			p = uintptr(sysReserve(unsafe.Pointer(p), pSize, &reserved))
 			if p != 0 {