Correct the copyright year in the "--version" output.

docs/DEVELOPERS.md

@@ -119,6 +119,7 @@ The package maintainer should run through these steps for a new release:
    * Check that `docs/TODO.md` is up to date
    * Check that the manual `docs/pv.1` is up to date
    * Run "`make docs/pv.1.md`" and, if using VPATH, copy the result to the source directory
+   * Check that the year displayed by src/main/version.c is correct
  * Ensure everything has been committed to the repository
  * Run "`autoreconf`" in the source directory
  * Consistency and build checks:

src/main/version.c

@@ -23,7 +23,7 @@ void display_version(void)
 	/* GNU standard first line format: program and version only */
 	printf("%s %s\n", PACKAGE_NAME, PACKAGE_VERSION);
 	/* GNU standard second line format - "Copyright" always in English */
-	printf("Copyright %s %s\n", "2023", "Andrew Wood");
+	printf("Copyright %s %s\n", "2024", "Andrew Wood");
 	/* GNU standard license line and free software notice */
 	printf("%s\n", _("License: GPLv3+ <https://www.gnu.org/licenses/gpl-3.0.html>"));
 	printf("%s\n", _("This is free software: you are free to change and redistribute it."));