bufio: suggest io.ReadFull at (*Reader).Read
bufio: suggest io.ReadFull at (*Reader).Read

Many times when using bufio.Reader I imagine, incorrectly, that it
implements the retry loop itself, being a high-level buffered wrapper
around, say, a file descriptor prone to short reads. This comment
would have saved me much time.

Change-Id: I34c790e0d7c1515430a76d02ce4739b586a36ba7
Reviewed-on: https://go-review.googlesource.com/c/145577
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

nawawi/go,nawawi/go,CAFxX/go,CAFxX/go,nawawi/go,akutz/go,akutz/go,josharian/go,golang/go,nawawi/go,nawawi/go,golang/go,akutz/go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,josharian/go,cloudflare/go,CAFxX/go,cloudflare/go,CAFxX/go,cloudflare/go,nawawi/go,golang/go,josharian/go,josharian/go,josharian/go,golang/go,akutz/go,akutz/go,akutz/go,cloudflare/go,josharian/go,CAFxX/go,josharian/go,akutz/go,CAFxX/go,golang/go,golang/go,cloudflare/go,nawawi/go,cloudflare/go,josharian/go,CAFxX/go,cloudflare/go,akutz/go,golang/go