runtime: fix build, rename a since-renamed hasprefix to hasPrefix

I merged CL 115835 without testing it after a rebase. My bad.

Change-Id: I0acc6ed78ea7d718ac2df11d509cfcf4364dfaee
Reviewed-on: https://go-review.googlesource.com/130815
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>

src/runtime/panic.go

@@ -37,7 +37,7 @@ var indexError = error(errorString("index out of range"))
 // entire runtime stack for easier debugging.
 
 func panicindex() {
-	if hasprefix(funcname(findfunc(getcallerpc())), "runtime.") {
+	if hasPrefix(funcname(findfunc(getcallerpc())), "runtime.") {
 		throw(string(indexError.(errorString)))
 	}
 	panicCheckMalloc(indexError)
@@ -47,7 +47,7 @@ func panicindex() {
 var sliceError = error(errorString("slice bounds out of range"))
 
 func panicslice() {
-	if hasprefix(funcname(findfunc(getcallerpc())), "runtime.") {
+	if hasPrefix(funcname(findfunc(getcallerpc())), "runtime.") {
 		throw(string(sliceError.(errorString)))
 	}
 	panicCheckMalloc(sliceError)