Introduce doing_filter() and doing_action() to identify hooks in progress.

did_action() returns true the moment a hook is initially run, leaving you no way to tell if the hook is still in progress. Hooks can be nested and this checks the entire stack, versus current_filter() which only identifies the final hook in the stack. This commit also introduces current_action() for parity.

To tell if a hook has completed, one can use did_action() and ! doing_action() together.

The functions do not require an argument. In that situation, they indicate whether the stack is empty.

props ericmann for the initial unit tests.
fixes #14994.


git-svn-id: https://develop.svn.wordpress.org/trunk@27294 602fd350-edb4-49c9-b593-d223f7449a82
More robust `.gitignore` file

fixes #27207. props TobiasBg, markjaquith.

git-svn-id: https://develop.svn.wordpress.org/trunk@27295 602fd350-edb4-49c9-b593-d223f7449a82
Set the taxonomy property in the WP_Adjacent_Post class. fixes #26937.


git-svn-id: https://develop.svn.wordpress.org/trunk@27296 602fd350-edb4-49c9-b593-d223f7449a82