Docs: LCL/various. Adds missing unit overview content, external references in:

* customdrawn_android.xml
* customdrawn_common.xml
* customdrawn_mac.xml
* customdrawn_winxp.xml
* customdrawncontrols.xml
* customdrawndrawers.xml

(cherry picked from commit f6555a287e)

docs/xml/lcl/customdrawn_android.xml

@@ -21,10 +21,35 @@ customdrawn_android
 -->
 
 <module name="customdrawn_android">
-<short></short>
+<short>
+Contains classes used to implement custom-drawn controls using the drawing 
+style for the Android platform.
+</short>
 <descr>
+<p>
+<file>customdrawn_android.pas</file> is part of the Lazarus Component Library 
+<b>(LCL)</b>.
+</p>
 </descr>
 
+<!-- external references -->
+<element name="classes"/>
+<element name="sysutils"/>
+<element name="types"/>
+<element name="math"/>
+<element name="fpcanvas"/>
+<element name="fpimgcanv"/>
+<element name="fpimage"/>
+<element name="graphics"/>
+<element name="controls"/>
+<element name="lcltype"/>
+<element name="lclintf"/>
+<element name="intfgraphics"/>
+<element name="lresources"/>
+<element name="forms"/>
+<element name="customdrawndrawers"/>
+<element name="customdrawn_common"/>
+
 <!-- class Visibility: default -->
 <element name="TCDDrawerAndroid">
 <short></short>

docs/xml/lcl/customdrawn_common.xml

@@ -21,10 +21,34 @@ customdrawn_common
 -->
 
 <module name="customdrawn_common">
-<short></short>
+<short>
+Contains the common base class for renders in custom-drawn controls.
+</short>
 <descr>
+<p>
+<file>customdrawn_common.pas</file> is part of the Lazarus Component Library 
+<b>(LCL)</b>.
+</p>
 </descr>
 
+<!-- external references -->
+<element name="classes"/>
+<element name="sysutils"/>
+<element name="types"/>
+<element name="math"/>
+<element name="fpcanvas"/>
+<element name="fpimage"/>
+<element name="lazutf8"/>
+<element name="graphics"/>
+<element name="controls"/>
+<element name="lcltype"/>
+<element name="stdctrls"/>
+<element name="comctrls"/>
+<element name="extctrls"/>
+<element name="forms"/>
+<element name="customdrawndrawers"/>
+<element name="extctrls"/>
+
 <!-- class Visibility: default -->
 <element name="TCDDrawerCommon">
 <short></short>

docs/xml/lcl/customdrawn_mac.xml

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="ISO-8859-1"?>
+<?xml version="1.0" encoding="UTF-8"?>
 <!--
 
 Documentation for LCL (Lazarus Component Library) and LazUtils (Lazarus 
@@ -21,10 +21,30 @@ CustomDrawn_Mac
 -->
 
 <module name="CustomDrawn_Mac">
-<short></short>
+<short>
+Contains classes used to implement custom-drawn controls using the macOS 
+drawing style.
+</short>
 <descr>
+<p>
+<file>customdrawn_mac.pas</file> is part of the Lazarus Component Library 
+<b>(LCL)</b>.
+</p>
 </descr>
 
+<!-- external references -->
+<element name="classes"/>
+<element name="sysutils"/>
+<element name="types"/>
+<element name="fpcanvas"/>
+<element name="fpimage"/>
+<element name="math"/>
+<element name="graphics"/>
+<element name="controls"/>
+<element name="lcltype"/>
+<element name="customdrawndrawers"/>
+<element name="customdrawn_common"/>
+
 <!-- class Visibility: default -->
 <element name="TCDDrawerMac">
 <short></short>

docs/xml/lcl/customdrawn_winxp.xml

@@ -21,10 +21,29 @@ customdrawn_winxp
 -->
 
 <module name="customdrawn_winxp">
-<short></short>
+<short>
+Contains classes used to implement custom-drawn controls using the Windows XP 
+drawing style.
+</short>
 <descr>
+<p>
+<file>customdrawn_winxp.pas</file> is part of the Lazarus Component Library 
+<b>(LCL)</b>.
+</p>
 </descr>
 
+<!-- external references -->
+<element name="classes"/>
+<element name="sysutils"/>
+<element name="types"/>
+<element name="fpcanvas"/>
+<element name="fpimage"/>
+<element name="graphics"/>
+<element name="controls"/>
+<element name="lcltype"/>
+<element name="customdrawndrawers"/>
+<element name="customdrawn_common"/>
+
 <!-- class Visibility: default -->
 <element name="TCDDrawerWinXP">
 <short></short>

docs/xml/lcl/customdrawncontrols.xml

@@ -21,10 +21,41 @@ customdrawncontrols
 -->
 
 <module name="customdrawncontrols">
-<short></short>
+<short>
+Contains classes used to implement custom-drawn components or controls.
+</short>
 <descr>
+<p>
+<file>customdrawncontrols.pas</file> is part of the Lazarus Component Library 
+<b>(LCL)</b>.
+</p>
+<p>
+Copyright (C) 2011 Felipe Monteiro de Carvalho.
+</p>
 </descr>
 
+<!-- external references -->
+<element name="classes"/>
+<element name="sysutils"/>
+<element name="contnrs"/>
+<element name="math"/>
+<element name="types"/>
+<element name="lazutf8"/>
+<element name="lcltype"/>
+<element name="lclproc"/>
+<element name="lclintf"/>
+<element name="lclmessageglue"/>
+<element name="lmessages"/>
+<element name="messages"/>
+<element name="forms"/>
+<element name="graphics"/>
+<element name="controls"/>
+<element name="stdctrls"/>
+<element name="extctrls"/>
+<element name="comctrls"/>
+<element name="buttons"/>
+<element name="customdrawndrawers"/>
+
 <!-- class Visibility: default -->
 <element name="TCDControl">
 <short></short>

docs/xml/lcl/customdrawndrawers.xml

@@ -21,10 +21,29 @@ customdrawndrawers
 -->
 
 <module name="customdrawndrawers">
-<short></short>
+<short>
+Contains classes and routines used to draw custom-drawn controls for various 
+platforms, operating systems, or user-specified styles.
+</short>
 <descr>
+<p>
+<file>customedrawndrawers.pas</file> is part of the Lazarus Component Library 
+<b>(LCL)</b>.
+</p>
 </descr>
 
+<!-- external references -->
+<element name="classes"/>
+<element name="sysutils"/>
+<element name="types"/>
+<element name="fpcanvas"/>
+<element name="fpimage"/>
+<element name="controls"/>
+<element name="graphics"/>
+<element name="comctrls"/>
+<element name="extctrls"/>
+<element name="lazutf8"/>
+
 <!-- constant Visibility: default -->
 <element name="CDDRAWSTYLE_COUNT">
 <short></short>