Update the version number in the man pages, not only the date.

maint/RELEASE_PROCEDURE

@@ -28,7 +28,8 @@ ${underscore_version} shall be replaced by something like 4_6
 === day 14 (official release) ===
 
 * Review the English version of the manual and fix it if necessary.
-  Update the date in the .TH macro of the English manual.
+  Update the date and the version number in the .TH macro of the English
+  manual pages.
 * Update the NEWS file to contain all user-visible changes.
 * Fix wrong formatting in the ChangeLog files.
 * Set the version number in configure.ac to "${dotted_version}".