go.crypto/salsa: fix typo in comment and move TODO out of package comment.

Thanks to Frithjof Schulze for noticing.

R=goland-dev, r
CC=golang-dev
https://golang.org/cl/11033044

salsa20/salsa20.go

@@ -5,7 +5,7 @@
 /*
 Package salsa20 implements the Salsa20 stream cipher as specified in http://cr.yp.to/snuffle/spec.pdf.
 
-Salsa20 differs from many other stream ciphers in that is message orientated
+Salsa20 differs from many other stream ciphers in that it is message orientated
 rather than byte orientated. Keystream blocks are not preserved between calls,
 therefore each side must encrypt/decrypt data with the same segmentation.
 
@@ -18,11 +18,11 @@ cipher.
 This package also implements XSalsa20: a version of Salsa20 with a 24-byte
 nonce as specified in http://cr.yp.to/snuffle/xsalsa-20081128.pdf. Simply
 passing a 24-byte slice as the nonce triggers XSalsa20.
-
-TODO(agl): implement XORKeyStream12 and XORKeyStream8 - the
-reduced round variants of Salsa20. */
+*/
 package salsa20
 
+// TODO(agl): implement XORKeyStream12 and XORKeyStream8 - the reduced round variants of Salsa20.
+
 import (
 	"code.google.com/p/go.crypto/salsa20/salsa"
 )