[css-syntax] CDC-token is ignored

In section 4.3.1, "Consume a token", under subsection "U+002D HYPHEN-MINUS
(-)", there is an unreachable portion of the algorithm.

The second paragraph here states:
"[...] if the input stream starts with an identifier, [...] consume an
ident-like token".

Section 4.3.10, "Check if three code points would start an identifier",
returns true when the first two code points are U+002D.

This means we can never reach the third paragraph (under the U+002D
subsection of 4.3.1) with the two U+002D code points needed for the
CDC-token.

Cheers!
Beau