Remove (path) usage from the CSS parser
Remove (path) usage from the CSS parser

This updates the CSS parser to make it compatible with the XPath AST
changes introduced in commit 365a9e9fa9ced28b52b8b1e4da20bd71f41d5c21.
This also, finally, means I can get rid of some of the hacks that were
used for "+ foo" selectors and building (path) nodes.

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