Themes: Allow template loading functions to pass additional arguments to the template via the $args parameter.
This affects:
* `get_header()`
* `get_footer()`
* `get_sidebar()`
* `get_template_part()`
* `locate_template()`
* `load_template()`
Note: `get_search_form()` already passes additional arguments to the template as of [44956].
Props enrico.sorcinelli, sc0ttkclark, scribu, nacin, wonderboymusic, GeertDD, beatpanda, amaschas, mintindeed, ysalame, caiocrcosta, bigdawggi, julianm, eddiemoya, shawnz, sayedwp, shamai, mboynes, mihai2u, guidobras, Mte90, apedog, stuffradio, overclokk, johnbillion, joyously, afercia, audrasjb, justlevine, SergeyBiryukov.
See #21676.
git-svn-id: https://develop.svn.wordpress.org/trunk@48370 602fd350-edb4-49c9-b593-d223f7449a82
4e78b0acd9