Unicode support and -gnatW8

[mosteo]

Before our next major release I think we need to explore all ramifications of including -gnatW8 by default in our projects (which at this time is enabled), and from that we should have an specific section in our documentation.

To put us in context: source files, string encoding, and identifier encoding in an Ada program have complex rules and a complex set of switches and interactions with Ada.Text_IO. Before going in there, in this opening post I will simply gather empirical output.

I've run alr test on our current index (commit dcb5bbe7) as-is, and with a forced -gnatW8. There is a limited number of new failures with the latter, and of those 4 are due to an error in a dependency and not the releases themselves:

FAIL:apdf=5.0.3
	pdf_out_demo.adb:70:54: illegal wide character
FAIL:awa=2.4.0
	asf-converters-numbers.adb:131:53: error: literal out of range of type Standard.Character
FAIL:awa_unit=2.4.0
	asf-converters-numbers.adb:131:53: error: literal out of range of type Standard.Character
FAIL:excel_writer=17.0.1
	excel_out_demo.adb:125:39: illegal wide character
	csv2html.adb:19:13: illegal wide character
FAIL:mandelbrot_ascii=1.0.0
	mandelbrot_ascii.adb:105:05: literal out of range of type Standard.Character
FAIL:pico_examples=2.0.0
	main.adb:34:70: error: literal out of range of type Standard.Character
FAIL:progress_indicators=0.0.1
	progress_indicators-bars.adb:32:46: literal out of range of type Standard.Character
FAIL:semantic_versioning=2.1.0
	semantic_versioning-demo.adb:101:47: literal out of range of type Standard.Character
FAIL:septum=0.0.7
	progress_indicators-bars.adb:32:46: literal out of range of type Standard.Character
FAIL:serverfaces=1.5.0
	asf-converters-numbers.adb:131:53: error: literal out of range of type Standard.Character
FAIL:serverfaces_unit=1.5.0
	asf-converters-numbers.adb:131:53: error: literal out of range of type Standard.Character
FAIL:simple_logging=1.2.0
	simple_logging.adb:121:25: literal out of range of type Standard.Character

This is Linux only.

So putting out new releases for those crates with -gnatW8 in their configuration would be doable effort. That aspect of the issue for me can be put to rest.

I intend to follow up with a set of observations on how -gnatW8 impacts the use of Ada.Text_IO and Ada.W_W_Text_IO, and from that derive the set of best practices to follow (besides using something like vss)

References:

• https://stackoverflow.com/a/72533446/761390
• https://docs.adacore.com/gnat_rm-docs/html/gnat_rm/gnat_rm/the_implementation_of_standard_i_o.html
• https://docs.adacore.com/live/wave/gnat_ugn/html/gnat_ugn/gnat_ugn/the_gnat_compilation_model.html#foreign-language-representation
• https://docs.adacore.com/live/wave/gnat_ugn/html/gnat_ugn/gnat_ugn/building_executable_programs_with_gnat.html#character-set-control