CKEditor library requirements checking is too strict; libraries can be located in profiles and individual site dirs as well

Problem/Motivation

In hook_requirements, edit checks that the CKEditor library is located in sites/all/libraries.

if (strpos(libraries_get_path('ckeditor'), 'sites/all/libraries') === FALSE) {

But a library can also be located under the profiles dir or a specific site dir.

Proposed resolution

The libraries_get_path method actually returns NULL if a library isn't located in a sanctioned directory. So we can assume that if libraries can't find the ckeditor plugin, then it's not in the right place.

User interface changes

None.

API changes

None.

Original report by @jessebeach