build: bump version to 1.12.3

- improve documentation / manpages
- add --reindex option to 'mu index'
- split off mu4e-complete-contact (for wider use)
- work around some mail rendering issues with some emacs version
- update some dependencies
- fix some build warnings on older emacsen
- fix musl build

meson.build

@@ -17,7 +17,7 @@
 ################################################################################
 # project setup
 project('mu', ['c', 'cpp'],
-        version: '1.12.2',
+        version: '1.12.3',
         meson_version: '>= 0.56.0',
         license: 'GPL-3.0-or-later',
         default_options : [
@@ -28,7 +28,7 @@ project('mu', ['c', 'cpp'],
 
 # hard-code the date here (for reproduciblity); we derive the dates used in e.g.
 # documentation from this.
-mu_date='2024-03-16'
+mu_date='2024-04-08'
 
 # installation paths
 prefixdir = get_option('prefix')