Revert "allow xml in module description"

This reverts commit a2c9587165.

Somehow the OCaml XML/DTD parser doesn't like it if the description contains CDATA...

conf/modules/gps_ubx_i2c.xml

@@ -4,12 +4,6 @@
   <doc>
     <description>
       U-blox GPS (I2C)
-      This module provides an I2C interface that can then be used in the gps_ublox module:
-@verbatim
-<module name="gps_ublox">
-  <configure name="UBX_GPS_PORT" value="gps_i2c"/>
-</module>
-@endverbatim
     </description>
     <configure name="GPS_UBX_I2C_DEV" value="i2cX" description="set i2c peripheral (default: i2c1)"/>
   </doc>

conf/modules/module.dtd

@@ -14,7 +14,7 @@
 <!ELEMENT datalink EMPTY>
 <!ELEMENT makefile (configure|define|flag|file|file_arch|raw)*>
 <!ELEMENT section (define|configure)*>
-<!ELEMENT description (#CDATA)>
+<!ELEMENT description (#PCDATA)>
 <!ELEMENT configure EMPTY>
 <!ELEMENT define EMPTY>
 <!ELEMENT flag EMPTY>

conf/modules/nav_survey_polygon.xml

@@ -15,7 +15,7 @@ In the flight plan, the survey blocks call init and run functions:
   - min_rad       minimal radius when navigating
   - altitude      the altitude that must be reached before the flyover starts
 2. Run the survey with nav_survey_polygon_run()
-
+<!--
 Block example:
 @verbatim
 <block name="Poly Survey" strip_button="Poly Survey">
@@ -23,6 +23,7 @@ Block example:
   <call fun="nav_survey_polygon_run()"/>
 </block>
 @endverbatim
+-->
     </description>
   </doc>
   <header>

conf/modules/nav_survey_rectangle_rotorcraft.xml

@@ -13,7 +13,7 @@ In the flight plan, the survey blocks call init and run functions:
   - sweep_width   distance between the sweeps
   - angle         NS or WE orientation
 2. Run the survey with nav_survey_rectangle_rotorcraft_run(WP1,WP2)
-
+<!--
 Block example:
 @verbatim
 <block name="Poly Survey" strip_button="Poly Survey">
@@ -25,11 +25,12 @@ or using flightplan primitive
   <survey_rectangle grid="30" orientation="NS" wp1="S1" wp2="S2"/>
 </block>
 @endverbatim
+-->
     </description>
     <define name="RECTANGLE_SURVEY_DEFAULT_SWEEP" value="25" description="default sweep distance when using dinamic setup"/>
   </doc>
-
-  <settings>
+  
+    <settings>
     <dl_settings>
       <dl_settings NAME="Ret_Survey">
         <dl_setting min="10" max="500" step="1" var="sweep" type="float" shortname="Distance" module="modules/nav/nav_survey_rectangle_rotorcraft"/>