go.crypto/ssh: remove misleading marshalPrivRSA.

Properly capitalize publicKey throughout.

R=golang-dev
CC=agl, dave, golang-dev, jpsugar
https://golang.org/cl/13415046
diff --git a/ssh/common.go b/ssh/common.go
index bbbb00e..3df556d 100644
--- a/ssh/common.go
+++ b/ssh/common.go
@@ -248,7 +248,7 @@
 }
 
 // serialize a *rsa.PublicKey or *dsa.PublicKey according to RFC 4253 6.6.
-func serializePublickey(key interface{}) []byte {
+func serializePublicKey(key interface{}) []byte {
 	var pubKeyBytes []byte
 	algoname := algoName(key)
 	switch key := key.(type) {
@@ -304,7 +304,7 @@
 			}
 		}
 	}
-	panic("unexpected key type")
+	panic(fmt.Sprintf("unexpected key type %T", key))
 }
 
 // buildDataSignedForAuth returns the data that is signed in order to prove