Fix a few comment typos.

address.go

@@ -40,7 +40,7 @@ func ExtractPkScriptAddrs(pkScript []byte, net btcwire.BitcoinNet) (ScriptClass,
 	case PubKeyTy:
 		// A pay-to-pubkey script is of the form:
 		//  <pubkey> OP_CHECKSIG
-		// Therefore the pubkey is the item on the stack.
+		// Therefore the pubkey is the first item on the stack.
 		// Skip the pubkey if it's invalid for some reason.
 		requiredSigs = 1
 		addr, err := btcutil.NewAddressPubKey(pops[0].data, net)

script.go

@@ -1122,7 +1122,7 @@ func signatureScriptCustomReader(reader io.Reader, tx *btcwire.MsgTx, idx int,
 
 // expectedInputs returns the number of arguments required by a script.
 // If the script is of unnown type such that the number can not be determined
-// then -1 is returned. We are an interanl function and thus assume that class
+// then -1 is returned. We are an internal function and thus assume that class
 // is the real class of pops (and we can thus assume things that were
 // determined while finding out the type).
 func expectedInputs(pops []parsedOpcode, class ScriptClass) int {

scriptbuilder.go

@@ -19,7 +19,7 @@ const (
 )
 
 // ScriptBuilder provides a facility for building custom scripts.  It allows
-// you to push opcodes, ints, and, data while respecting canonical encoding.  It
+// you to push opcodes, ints, and data while respecting canonical encoding.  It
 // does not ensure the script will execute correctly.
 //
 // For example, the following would build a 2-of-3 multisig script for usage in