Fix indentation of multiline CSS property values

Fix indentation of multiline CSS property values

* lisp/textmodes/css-mode.el (css-smie-grammar): Give colons belonging
to properties higher precedence.
(css--colon-inside-selector-p, css--colon-inside-funcall): New
functions for helping SMIE during tokenization.
(css-smie--forward-token, css-smie--backward-token): Distinguish
colons belonging to properties from other colons.

* test/manual/indent/css-mode.css: Add tests for the changes above.

* test/manual/indent/scss-mode.scss: Ditto.