Minor documentation fixes

* Remove duplicated Interface Kit description.
* Fixed links, a typo, inconsistent page names.

Change-Id: I38e5943f31bf30870d33f02a97b4ef899222ec36
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4854
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: Adrien Destugues <[email protected]>

docs/user/app/_app_messaging.dox

@@ -104,7 +104,7 @@
 	If your handler cannot handle the object, it will pass the message on to
 	the parent class. 
 
-	\warning Don't forget to actuall call the MessageReceived() method of the
+	\warning Don't forget to actually call the MessageReceived() method of the
 		base class. Failing to do this will mean that the message chain will
 		not completely be followed, which can lead to unhandled messages. There
 		might be some internal system messages that the Haiku API classes

docs/user/book.dox

@@ -125,26 +125,6 @@
 	\defgroup interface Interface Kit
 	\brief API for displaying a graphical user interface.
 
-	The Interface Kit holds all the classes you'll need to develop a GUI.
-	Building on the messaging facilities provided by the Application Kit,
-	the Interface Kit can be used to create a responsive and attractive
-	graphical user interface.
-
- 	The most important class in the Interface Kit is the BView class, which
-	handles drawing and user interaction. Pointer and keyboard events are
-	processed in this class.
-
-	Another important class is the BWindow class, which holds BViews and makes
-	them visible to the user. The BWindow class also handles BView focusing
-	and BMessage dispatching, among other things.
-
-	A new addition Haiku has added over the BeOS API is the Layout API, which
-	is based around the BLayoutItem and BLayout classes. These classes will
-	take care of making sure all your GUI widgets end up where you want them,
-	with enough space to be useful. You can start learning the Layout API
-	by reading the \link layout_intro introduction \endlink.
-
-
 	\defgroup locale Locale Kit
 	\brief Collection of classes for localizing applications.
 

docs/user/interface/_interface_intro.dox

@@ -30,13 +30,13 @@
 	is based around the BLayoutItem and BLayout classes. These classes will
 	take care of making sure all your GUI widgets end up where you want them,
 	with enough space to be useful. You can start learning the Layout API 
-	by reading the \link layout_intro introduction \endlink.
+	by reading the \ref layout_intro.
 
-	\section Coordinate spaces
+	\section coordinatespaces Coordinate spaces
 
-	All APIs using coordinates (such as \link BRect or \link BPoint ) refer to
+	All APIs using coordinates (such as BRect or BPoint) refer to
-	a specific space where these coordinates are interpreted. \link BView and
+	a specific space where these coordinates are interpreted. BView and
-	\link BWindow provide various conversion function to translate coordinates
+	BWindow provide various conversion function to translate coordinates
 	between different spaces, as needed, or provide separate methods such as
 	BView Bounds() and Frame(), returning results in different spaces as needed.
 

docs/user/interface/_layout_intro.dox

@@ -9,7 +9,7 @@
 
 
 /*!
-	\page layout_intro Introducing the Layout API.
+	\page layout_intro Introduction to the Layout API
 
 	Haiku's Layout API is centered around the BLayoutItem and BLayout classes.
 	The BLayoutItem class represents thing that can be managed by a BLayout,

docs/user/interface/layout_tips.dox

@@ -1,5 +1,5 @@
 /*!
-	\page layout_tips
+	\page layout_tips Layout API tips
 
 	\section layout_window_tips BWindow Tips