Copyright years: updated to 2023, accompanied by some minor fixes

SUMMARY: just house-cleaning, no need to do anything major in your
branch. Just update the copyright years in files that you have added.

Until now, the latest copyright years of the whole Maneage source code was
2022! As of this commit, we have already moved to 2023 for 5 months!
Furthermore, there were a few other minor issues that needed correction:

 - The URL to download input datasets wasn't quoted in 'initialize.mk' or
   the download script! As a result, when the input URL had characters that
   are meaningful to the shell (like '&'), the download command would not
   work.

 - The only program that had 'make check' in the 'basic.mk' programs was
   MPFR. At that stage, we still haven't built our own compiler at this
   stage, this is not accurate.

 - The 'pyerfa' and 'extension-helpers' packages in Python need
   'setuptools_scm' on some systems. But until now, it was not in the list
   of their prerequisites.

With this commit, all the issues above have been corrected.

8 files changed, 8 insertions, 8 deletions

diff --git a/tex/src/delete-me-image-histogram.tex b/tex/src/delete-me-image-histogram.tex
index 4648fe6..37618ec 100644
--- a/tex/src/delete-me-image-histogram.tex
+++ b/tex/src/delete-me-image-histogram.tex
@@ -1,6 +1,6 @@
 %% Plot the demonstration image and its histogram.
 %
-%% Copyright (C) 2019-2022 Mohammad Akhlaghi <mohammad@akhlaghi.org>
+%% Copyright (C) 2019-2023 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 %
 %% This file is free software: you can redistribute it and/or modify it
 %% under the terms of the GNU General Public License as published by the
diff --git a/tex/src/delete-me-squared.tex b/tex/src/delete-me-squared.tex
index f8e29cc..968b4d7 100644
--- a/tex/src/delete-me-squared.tex
+++ b/tex/src/delete-me-squared.tex
@@ -1,6 +1,6 @@
 %% PGFPlots code to plot a random set of numbers as demo
 %%
-%% Copyright (C) 2019-2022 Mohammad Akhlaghi <mohammad@akhlaghi.org>
+%% Copyright (C) 2019-2023 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 %
 %% This file is free software: you can redistribute it and/or modify it
 %% under the terms of the GNU General Public License as published by the
diff --git a/tex/src/preamble-biblatex.tex b/tex/src/preamble-biblatex.tex
index 2ac18d9..fd4bf9d 100644
--- a/tex/src/preamble-biblatex.tex
+++ b/tex/src/preamble-biblatex.tex
@@ -12,7 +12,7 @@
 %%     helps in clearly identifying the files and avoiding places that
 %%     complain about '.bib' files.
 %
-%% Copyright (C) 2018-2022 Mohammad Akhlaghi <mohammad@akhlaghi.org>
+%% Copyright (C) 2018-2023 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 %
 %% This file is free software: you can redistribute it and/or modify it
 %% under the terms of the GNU General Public License as published by the
diff --git a/tex/src/preamble-maneage-default-style.tex b/tex/src/preamble-maneage-default-style.tex
index 10a61ad..f811743 100644
--- a/tex/src/preamble-maneage-default-style.tex
+++ b/tex/src/preamble-maneage-default-style.tex
@@ -6,7 +6,7 @@
 %% style defined here as a preamble. To ignore it, uncomment or delete the
 %% respective line in 'paper.tex'.
 %
-%% Copyright (C) 2019-2022 Mohammad Akhlaghi <mohammad@akhlaghi.org>
+%% Copyright (C) 2019-2023 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 %
 %% This file is free software: you can redistribute it and/or modify it
 %% under the terms of the GNU General Public License as published by the
diff --git a/tex/src/preamble-maneage.tex b/tex/src/preamble-maneage.tex
index 6875e37..5dc89fe 100644
--- a/tex/src/preamble-maneage.tex
+++ b/tex/src/preamble-maneage.tex
@@ -1,6 +1,6 @@
 %% Preamble for Maneage-related features.
 %
-%% Copyright (C) 2020-2022 Mohammad Akhlaghi <mohammad@akhlaghi.org>
+%% Copyright (C) 2020-2023 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 %
 %% This LaTeX file is part of Maneage. Maneage is free software: you can
 %% redistribute it and/or modify it under the terms of the GNU General
diff --git a/tex/src/preamble-pgfplots.tex b/tex/src/preamble-pgfplots.tex
index c200845..86f649c 100644
--- a/tex/src/preamble-pgfplots.tex
+++ b/tex/src/preamble-pgfplots.tex
@@ -40,7 +40,7 @@
 %%    hasn't changed since the last build. TiKZ/PGFPlots won't rebuild the
 %%    plot.
 %
-%% Copyright (C) 2018-2022 Mohammad Akhlaghi <mohammad@akhlaghi.org>
+%% Copyright (C) 2018-2023 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 %
 %% This file is part of Maneage (https://maneage.org).
 %
diff --git a/tex/src/preamble-project.tex b/tex/src/preamble-project.tex
index a596aec..76603f2 100644
--- a/tex/src/preamble-project.tex
+++ b/tex/src/preamble-project.tex
@@ -4,7 +4,7 @@
 %% LaTeX usages. However, if any are not needed in your work, please feel
 %% free to remove them.
 %
-%% Copyright (C) 2018-2022 Mohammad Akhlaghi <mohammad@akhlaghi.org>
+%% Copyright (C) 2018-2023 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 %% Copyright (C) YYYY Your Name <your@email.address>
 %
 %% This file is free software: you can redistribute it and/or modify it
diff --git a/tex/src/references.tex b/tex/src/references.tex
index 267b9ab..e4117ae 100644
--- a/tex/src/references.tex
+++ b/tex/src/references.tex
@@ -1,7 +1,7 @@
 %% Non-software BibTeX entries. The software-specific BibTeX entries are
 %% stored in a '*.tex' file under the 'tex/dependencies' directory.
 %
-%% Copyright (C) 2018-2022 Mohammad Akhlaghi <mohammad@akhlaghi.org>
+%% Copyright (C) 2018-2023 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 %
 %% Copying and distribution of this file, with or without modification,
 %% are permitted in any medium without royalty provided the copyright