Split paths portability

[William A. Rowe, Jr.]

While we consider Stas' ideas for a portable tmpdir, we should also consider
breaking apart path strings (such as env('PATH'), or LIB or INCLUDE paths
as well.)  These semantics change considerably from Win32 to unix and
other platforms.  I dunno what NetWare does here, anymore.
Two options; the one I like best (I think) is returning an apr_array_header_t *
allocated based on a pool arg.  Contrawise, we should also have a function
that returns a char* from an apr_array_header_t.  Something like;
  apr_array_header_t *apr_filepath_list_split(const char *pathlist, 
apr_pool_t *pool);
  char *apr_filepath_list_join(apr_array_header_t *paths, apr_pool_t *pool);

Any objections?
Bill