Moved prototypes/defines for ap_os_canonical_filename(),

ap_os_case_canonical_filename(), ap_os_systemcase_filename(), and
ap_os_is_filename_valid() from httpd.h to the separate os.h files.
Moved BS2000-specific os_set_account() and os_init_job_environment()
prototypes to bs2000/os.h.  HAVE_CANONICAL_FILENAME no londer needed.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@82614 13f79535-47bb-0310-9956-ffa450edef68