Add mono mode recording setting to manual

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@18747 a1c6a512-1295-4272-9138-f99709370657
diff --git a/manual/configure_rockbox/recording_settings.tex b/manual/configure_rockbox/recording_settings.tex
index 4135398..15e0b1f 100644
--- a/manual/configure_rockbox/recording_settings.tex
+++ b/manual/configure_rockbox/recording_settings.tex
@@ -81,6 +81,12 @@
   for mono recording, only the left channel is recorded. Mono recordings
   are usually somewhat smaller than stereo.
 
+\opt{swcodec}{
+  \section{Mono Mode}
+    When configured to record to mono and the source is a stereo signal, use this
+    setting to configure how the mono signal is created. Options are L, R and L+R.
+}
+
 \opt{MASCODEC}{
   \section{Independent Frames}
     The independent frames option tells the \dap{} to encode with the bit