Give :property nodes a :children array.

It contains all the nodes that make up the property's value.
Typo.
Don't choke when consuming a non-token :function

This could occur when parsing the body of a @media rule as a list of
rules. Since :function nodes have already been parsed in this case,
treating them as if they're :function *tokens* results in the rest of
the token stream being consumed, which sucks.