Docs: LCL/dialogs, LCL/extdlgs. Updates content in Filter topics, including:

* TFileDialog.Filter
* TOpenPictureDialog.Filter

(cherry picked from commit 1fcfe24d7d)

docs/xml/lcl/dialogs.xml

@@ -1236,19 +1236,22 @@ classes. For example, it represents a directory name in the
 
 <element name="TFileDialog.Filter">
 <short>
-A string which contains possible filename filters (e.g. .doc, .xmp, .pas etc).
+A string which contains available filename filters used to select files by 
+their file extensions.
 </short>
 <descr>
 <p>
-This is a string which contains the filters a user can choose from. The 
-available filters and their description are separated by pipe symbols.
+This is a string which contains the filters a user can choose from. The filters 
+contain descriptive text for the filters and their file masks. The component 
+values in the filter are separated by the Pipe (|) symbol.
 </p>
 <p>
-To set this property at run-time assign a value like:
+A value can be assigned to the property using notation like:
 </p>
 <code>'All files|*.*|Lazarus Project files|*.lpr'</code>
 <p>
-An entry can contain multiple masks separated by semicolon, like:
+A filter can contain multiple file masks separated by the Semicolon (;) 
+character, like:
 </p>
 <code>'Pascal units|*.pas;*.pp;*.p|All files|*.*'</code>
 </descr>

docs/xml/lcl/extdlgs.xml

@@ -632,8 +632,11 @@ in the dialog.
 list of file name filters available in the dialog. Each value in the 
 delimited list is separated by a Pipe (or vertical bar) character ('|') and 
 consists of a description and file extension for files matching the filter 
-value.
+value. For example:
 </p>
+<code>
+'All files|*.*|Lazarus Project files|*.lpr|Pascal units|*.pas;*.pp'
+</code>
 <p>
 The initial value for Filter is assigned in <var>Create</var> using the value 
 from the <var>DefaultFilter</var> property.