deb-triggers(5): explain better why {interest,activate}-noawait should be favored

Christoph Biedl asked me in #762031 to integrate more explanations why
the *-noawait directives should be preferred.

debian/changelog

@@ -1,5 +1,9 @@
 dpkg (1.17.14) UNRELEASED; urgency=low
 
+  [ Raphaël Hertzog ]
+  * Explain better in deb-triggers(5) why interest/activate-noawait should be
+    favored.
+
   [ Updated manpages translations ]
   * German (Helge Kreutzmann).
 

man/deb-triggers.5

@@ -1,7 +1,7 @@
 .\" dpkg manual page - deb-triggers(5)
 .\"
 .\" Copyright © 2008, 2013 Guillem Jover <guillem@debian.org>
-.\" Copyright © 2011 Raphaël Hertzog <hertzog@debian.org>
+.\" Copyright © 2011, 2014 Raphaël Hertzog <hertzog@debian.org>
 .\"
 .\" This is free software; you can redistribute it and/or modify
 .\" it under the terms of the GNU General Public License as published by
@@ -77,6 +77,13 @@ versions of the package will be activated.
 Unknown directives are an error which will prevent installation of the
 package.
 .PP
+The "\-noawait" variants should always be favored when possible since
+triggering packages are not put in triggers\-awaited state and can thus
+be immediately configured without requiring the processing of the trigger.
+If the triggering packages are dependencies of other upgraded packages,
+it will avoid an early trigger processing run and make it possible
+to run the trigger only once as one of the last steps of the upgrade.
+.PP
 The "\-noawait" variants are only supported since dpkg 1.16.1, and
 will lead to errors if used with an older dpkg. It is thus recommended
 to add a "Pre\-Depends: dpkg (>= 1.16.1)" to any package that wish to use