* cli/gcdmodel.cpp: Fix typos in comments.

* cli/gcdmodel.cpp (CGcdData::fixModelAndSubmodelOrder): Fix typos in comments.

* cli: Support "max" as an alias to the maximum value for the order switch.

* cli/cmdline.cpp (parseArg): Understand "all" for the order switch.
(showUsage): Document it.
* cli/gcdmodel.cpp (CGcdData::fixModelAndSubmodelOrder): Ensure the
root model order gets recomputed when "/o:max" was provided as argument.
* cli/model.h (UNDEFINED_ORDER): Redefine as the minimum int value.
(MAXIMUM_ORDER): New constant.
* doc/pict.md: Document it.
* test/arg/.tests: Add test.

Co-authored-by: Maxim Cournoyer <maxim.cournoyer@savoirfairelinux.com>

Multi-byte I/O dose too match for text input in some locale.

For example, "," in numbers treat as decimal separator, not word separator.
This makes "1,234" as "1234", not "1" and "234".

Use "C.UTF-8" to avoid this problem.

* Use UTF-8 for multi-byte character I/O everywhare

This fix is required for "libstdc++".
Without this fix, "libstdc++" only works for 7bit ASCII.

It fixes https://github.com/microsoft/pict/issues/24 .

* Use current locale instead of fixed UTF-8 locale

It is good for non-UTF-8 (ANSI/OEM) encoding input.
Use environment variable "LANG" or "LC_CTYPE" to change input encoding.

(example)
$ LC_CTYPE="C.UTF-8" pict utf8-input.txt

* Add document for non-ASCII (UTF-8/ANSI) input encoding

A white space must follows `#` in GitHub

In submodels, no parameter named IE