manual: document 3D enhancement

3D "enhancement" is available on all imx233 platform, and also on platforms
with the WM8978 codec (gigabeats) and WM8750 codec (MPIO HD 200/300). I used
different texts for different codecs because (in theory) they do different
"things".

Change-Id: I62ecb075f7594427491b6be83cfa80f763566aba

manual/configure_rockbox/sound_settings.tex

@@ -189,6 +189,20 @@ change to customise your listening experience.
   the effect of widening the stereo field. A value of 100\% will leave the
   stereo field unaltered.
 
+\opt{depth_3d}{
+  \section{3D Enhancement}
+  3D Enhancement increases the perceived separation between the left and right
+  channels.
+  \opt{IMX233}{%
+    It works by subtracting a portion of the opposite channel's content for each
+    channel. This setting controls the amount of opposite channel content that
+    is subtracted. A value of 0dB leaves the audio signal unmodified.}%
+  \opt{HAVE_WM8750,HAVE_WM8978}{%
+    This settings controls the degree of stereo expansion. A value of 0\%
+    leaves the audio signal unmodified.
+  }%
+}
+
 \opt{masf}{
   \section{Loudness}
   When listening at low volumes, the ear will tend to make bass and treble

manual/platform/gigabeats.tex

@@ -8,6 +8,7 @@
 \edef\UseOption{\UseOption,gigabeat}
 \edef\UseOption{\UseOption,GIGABEAT_RC_PAD}
 \edef\UseOption{\UseOption,HAVEREMOTEKEYMAP}
+\edef\UseOption{\UseOption,HAVE_WM8978}
 
 \newcommand{\playerman}{Toshiba}
 \newcommand{\playertype}{Gigabeat S Series}

manual/platform/mpiohd200.tex

@@ -8,6 +8,7 @@
 \edef\UseOption{\UseOption,mpio}
 \edef\UseOption{\UseOption,MPIO_RC_HD200_PAD}
 \edef\UseOption{\UseOption,HAVEREMOTEKEYMAP}
+\edef\UseOption{\UseOption,HAVE_WM8750}
 
 \newcommand{\playerman}{MPIO}
 \newcommand{\playertype}{HD200}

manual/platform/mpiohd300.tex

@@ -6,6 +6,7 @@
 \edef\UseOption{\UseOption,HAVE_DISK_STORAGE}
 \edef\UseOption{\UseOption,HAVE_CAR_ADAPTER_MODE}
 \edef\UseOption{\UseOption,mpio}
+\edef\UseOption{\UseOption,HAVE_WM8750}
 
 \newcommand{\playerman}{MPIO}
 \newcommand{\playertype}{HD300}