getopt.m4sh generated libtool option parser, and XSI improvements.

getopt.m4sh generated libtool option parser, and XSI improvements.

* libltdl/m4/libtool.m4 (_LT_PROG_XSI_SHELLFNS): Moved portable
shell versions of various utility functions from here...
* libltdl/config/getopt.m4sh (func_split_long_opt): ...to here...
* libltdl/config/general.m4sh (func_dirname, func_basename)
(func_dirname_and_basename, func_strip_name): ...here...
* libltdl/config/ltmain.m4sh (func_append, func_arith, func_len)
(func_lo2o, func_xform): ...and here.
* libltdl/config/libtool.m4 (_LT_PROG_XSI_REPLACE): New macro that
expands into a sed command for replacing the contents of a
suitably decorated shell function with an alternate XSI
implementation.
(_LT_PROG_XSI_SHELLFNS): Use it to replace the portable shell
versions of the functions above with equivalent XSI
implementations that avoid unnecessary forks if the host shell
supports that.
* libltdl/config/ltmain.m4sh: Replace hand written shell code
with a call to M4SH_GETOPTS. Rename some option variables in
the client code to match the generated option parser settings.
* libltdl/config/general.m4sh (func_echo, func_error)
(func_warning): Use $opt_mode instead of obsoleted $mode in
message leader.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>