Add an "eval" rule to Remarkup
Ref T13658. This adds a simple expression evaluator to Remarkup and supports platform name expressions. The syntax is:
Note that this won't work inside code blocks (or literal blocks, or other block-level literal elements) right now, although it could be made to selectively (the ".path" expressions might be useful in documentation codeblocks).
Reviewed By: cspeckmim
Maniphest Tasks: T13658
Differential Revision: https://secure.phabricator.com/D21713