version: add reminder comment for adding version macros to configure.ac

configure.ac

 AC_PREREQ([2.63])
 
 dnl The NM version number
+dnl
+dnl XXX: When incrementing version also:
+dnl  - add corresponding NM_VERSION_x_y_z macros in
+dnl    "shared/nm-version-macros.h.in"
+dnl  - update number in meson.build
 m4_define([nm_major_version], [1])
 m4_define([nm_minor_version], [11])
 m4_define([nm_micro_version], [1])

meson.build

 project(
   'NetworkManager', 'c',
+# XXX: When incrementing version also:
+#  - add corresponding NM_VERSION_x_y_z macros in
+#    "shared/nm-version-macros.h.in"
+#  - update number in configure.ac
   version: '1.11.1',
   license: 'GPL2+',
   default_options: [