net,mime: Minor corrections to documentation comments.

R=r
CC=dsymonds, gobot, golang-dev
https://golang.org/cl/6495085

src/pkg/mime/multipart/multipart.go

@@ -71,7 +71,7 @@ func (p *Part) parseContentDisposition() {
 	}
 }
 
-// NewReader creates a new multipart Reader reading from r using the
+// NewReader creates a new multipart Reader reading from reader using the
 // given MIME boundary.
 func NewReader(reader io.Reader, boundary string) *Reader {
 	b := []byte("\r\n--" + boundary + "--")

src/pkg/net/mail/message.go

@@ -47,7 +47,8 @@ type Message struct {
 }
 
 // ReadMessage reads a message from r.
-// The headers are parsed, and the body of the message will be reading from r.
+// The headers are parsed, and the body of the message will be available
+// for reading from r.
 func ReadMessage(r io.Reader) (msg *Message, err error) {
 	tp := textproto.NewReader(bufio.NewReader(r))