[go-nuts] Replace character with rune in the specification

A specific example where the dual usage has caused confusion is in the
first paragraph of the Constants section:
There are no character constants.
http://golang.org/ref/spec#Constants

Depending on the context, sure there are/were (just apparently not distinct
from 'rune literals').

http://play.golang.org/p/P51mgAvi1Z

I think some of the confusion will come from the untyped nature of rune
literals, since rune is a type, but char or character is not (in Go, at
least). As with C, anything in single quotes is interpreted to be an
integer of some value (if valid), and since rune literals are untyped
integers, they can be assigned to any integer type (hence being able to
assign a unicode codepoint sequence [in the range 0-255] to a byte variable
without conversion, despite the apparent semantic absurdity).

Here, 'character constant' (or more precisely, 'character literal'), would
not have the type ambiguity that 'rune literal' would, and may therefore be
less absurd. After all, runes are characters in the computational
linguistic sense, and if you're storing a single-quoted constant value into
a byte, you're certainly treating that byte value as non-binary data (since
you're giving it a glyph), so you're artificially imposing the 'character'
terminology on yourself again.

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