On calc versions and releases

Calc version numbers have 4 levels.  For example:

	 ++=== top 2 levels: calc builtin functions compatibility
	 ||
	vvvv

	2.14.0.8
	 \\\\\\
	^  \\\\----> top 3 levels: calc important code base change
	|
	+--- top version level: internal representation compatibility

The top version level (e.g., 2) refers to the internal representation
of values.  Any library or hardware linked/built for calc 2 will be able
to use values from other 2.x.y.z versions.

The top 2 levels (e.g., 2.14) refers to a specific compatible set of
builtin functions.  Calc interpreted code (such as calc resource files)
written for, say calc 2.14, will be able to use the same set of builtin
functions for any other 2.14.y.z version.  Any new builtin functions or
significant changes to existing builtin functions would be introduced in
a later release such as version 2.15.y.z.  While calc scripts written for
2.14.y.z will highly likely be able to run under version 2.15.y.z, any
new builtin functions added in calc 2.15 may collide with an identically
named used defined function.

The top 3 levels (e.g., 2.14.0) change to reflect an important change to
the code base such as a bug fix or performance improvement.  There was
neither a change to the internal representation format (a top level
version change), nor were there new calc builtins introduced in such
a top 3 level release.

There are 3 classes of changes to the calc source tree:

alpha		=> untagged GitHub commit

	Any untagged commit to the GitHub master branch should be
	considered as alpha code that may make calc unstable.

	While we try to avoid breaking the calc code with commits,
	there is a risk that picking up such a change could
	negatively impact the code.

tested		=> tagged GitHub pre-release commit

	A new version of calc has been released and has recently passed
	regression testing on at least to different platforms and chip
	architectures.

	The "tested" class was historically called "untested",
	however this term was misleading as such releases ARE tested.
	Since 2.14.0.13 we have used the term "tested".

	All tested releases are tagged with a new version number.
	Such releases have GitHub assets such as a source tarball,
	zip file, source rpm, development rpm and binary rpm.  See the
	orange "Pre-release" GitHub releases under:

	    https://github.com/lcn2/calc/releases

	 At the bottom of a given release is a "> Assets" that may
	 be opened to reveal down-loadable files.

production	=> tagged GitHub release commit

	A new version of calc has been released and has undergone
	extensive testing over time over a number of platforms.
	Sometimes a "tested" release that is found work well over
	a period of time will be re-released with a new version
	number as a "production" release.

	The latest production GitHub release is marked with green
	"Latest" label under:

	    https://github.com/lcn2/calc/releases

	A release that has neither an orange "Pre-release" nor
	a green "Latest" label is a prior production class release.

	At the bottom of a given release is a "> Assets" that may
	be opened to reveal down-loadable files.

	Production class code where stability is critical should use a
	"production" release.

A historical note and apology:

In the past, some version number changes were made that did not fully
reflect the above version number or change class.  Moreover older terms
such as "stable" and "unstable" were misleading and did not properly
reflect the nature of the change.  Sorry!  The purpose of this document
is to try and bring a better level of conformity to source code updates,
tagged releases and version numbers.

## Copyright (C) 2021  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
##
## Under source code control:	2021/12/12 19:36:26
## File existed as early as:	2021
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/
