[css21][css3-font] syntax identify of font-weight's 100 ~ 900 values

While reviewing css3 V&U, I found an interesting syntax corner case
related to whether 'font-weight's 100 ~ 900 values are more
<integer>-like or IDENT-like. The following declarations

A. 'font-weight: +700;'

B. 'font-weight: \37 00;' (CSS escaping)

have the following results

Firefox 11: only A applies
Chromium 18: both A and B apply
(the fact that B applies seems like a bug)
IE 9 and IE8 standards mode: only B applies
IE 7 standards mode and quirks mode: neither applies
(CSS escaping not supported, it seems)
Opera12alpha: only A applies

CSS 2.1 says nothing about this but the natural interpretation of the
current "Value:" line seems to be "neither apples".

I don't have a strong opinion but I suggest we match IE8 and above here.
That way, we don't need to worry whether and how calc() or attr as
integer applies in 'font-weight'. (I don't think implementers would be
be happy to implement something that's neither IDENT nor <number>.)


Cheers,
Kenny