functionality, use 8192 as a fallback if PATH_MAX is undefined.

* configure.ac: Check for canonicalize_file_name.

* commands.c (get_file_or_folder): Use canonicalize_file_name
instead of realpath.
(put_file_or_folder): Dito.

* gnu_stuff.c: Added compability function for systems without
canonicalize_file_name.

* gnu_stuff.h: Declaration of compability function.

* str_utils.h: Changed declaration of lsftp_s_strtok, take a char** to
fill in with a new allocated string instead of a buffer and it's
length.

* str_utils.c (lsftp_s_strtok): See above.

* commands.c: Changed to use the new lsftp_s_strtok.

* rl.c (lsftp_rl_completion): Dito.

* sftp_bind.c (lsftp_open_connection): Dito.

Rev: src/sftp/ChangeLog:1.31
Rev: src/sftp/commands.c:1.11
Rev: src/sftp/configure.ac:1.12
Rev: src/sftp/gnu_stuff.c:1.5
Rev: src/sftp/gnu_stuff.h:1.3
Rev: src/sftp/rl.c:1.6
Rev: src/sftp/sftp_bind.c:1.11
Rev: src/sftp/str_utils.c:1.3
Rev: src/sftp/str_utils.h:1.3