net/http: clarify semantics of File methods
net/http: clarify semantics of File methods

There were no docs explaining the meaning of Readdir's count
argument, for instance. Clarify that these mean the same as
the methods on *os.File.

R=golang-codereviews, minux.ma
CC=golang-codereviews
https://codereview.appspot.com/51630043

apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang