Set version in scrips using meson's configure_file [#52]

To avoid the issue of forgetting to bump them when releasing a new
version.  Which I've been doing for the last few versions.

Author: plattfot

baksnapper.sh

@@ -127,7 +127,7 @@ Fredrik "PlaTFooT" Salomonsson
 EOF
 
 read -rd '' version <<EOF
-baksnapper (baksnapper) 2.3.0
+baksnapper (baksnapper) @VERSION@
 Copyright (C) 2015-2025  Fredrik Salomonsson
 Copyright (C) 2021       Nathan Dehnel
 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.

baksnapperd-denotebak.sh

@@ -7,7 +7,7 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 read -rd '' version <<EOF
-baksnapperd-denotebak (baksnapper) 2.4.0
+baksnapperd-denotebak (baksnapper) @VERSION@
 Copyright (C) 2025  Fredrik Salomonsson
 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
 This is free software: you are free to change and redistribute it.

baksnapperd.sh

@@ -9,7 +9,7 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 read -rd '' version <<EOF
-baksnapperd (baksnapper) 2.4.0
+baksnapperd (baksnapper) @VERSION@
 Copyright (C) 2015-2025  Fredrik Salomonsson
 Copyright (C) 2021-2022  Nathan Dehnel
 Copyright (C) 2023       Juergen Gleiss