escape_shell_cmd was O(n^2), fix that.

tweak os_escape_path and escape_path_segment
remove some old code that was #if 0


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80527 13f79535-47bb-0310-9956-ffa450edef68