runtime: rename gothrow to throw

Rename "gothrow" to "throw" now that the C version of "throw"
is no longer needed.

This change is purely mechanical except in panic.go where the
old version of "throw" has been deleted.

sed -i "" 's/[[:<:]]gothrow[[:>:]]/throw/g' runtime/*.go

Change-Id: Icf0752299c35958b92870a97111c67bcd9159dc3
Reviewed-on: https://go-review.googlesource.com/2150
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>
diff --git a/src/runtime/stubs.go b/src/runtime/stubs.go
index 03e3ee9..591ece6 100644
--- a/src/runtime/stubs.go
+++ b/src/runtime/stubs.go
@@ -59,7 +59,7 @@
 func systemstack(fn func())
 
 func badsystemstack() {
-	gothrow("systemstack called from unexpected goroutine")
+	throw("systemstack called from unexpected goroutine")
 }
 
 // memclr clears n bytes starting at ptr.