* [FIX] Various fixes upon loading some of the subprojects: sync to recent PGC rewrites.
* [SC] Renamed all '...'-atoms to ...-variants.

* [FILE_EXT,NEW] Added last_path_component/2 which returns either the base name (for files) or the last subdirectory name (for directories).
* [HTML,NEW] Added html_pair//[2,3].
* [TMS_PRINT,FIX] Typo.
* [URI_EXT,EXT] Rewrite of download_to_file/3, adding option force/1 for skipping or re-downloading.
* [URI_EXT,EXT] Rewrite of url_to_file_name/2 no longer using the dubious name `dummy` for directory files.