Streamline the manual's Preface material

(The principle here is that Preface should only contain
meta-information about the manual, such as how to use it and who wrote
it; plus any political points that we want to draw attention to.)

* doc/ref/preface.texi (Preface): Make unnumbered, for consistency
  with other GNU manuals (e.g. Emacs, GSL).  Merge layout text into
  top level.  Simplify first sentence.  Move section on conventions
  away...

* doc/ref/intro.texi (Introduction to Guile): ...to here.

doc/ref/intro.texi

@@ -12,6 +12,7 @@
 * Obtaining and Installing Guile::  
 * Whirlwind Tour::              
 * Discouraged and Deprecated::
+* Manual Conventions::          
 * Reporting Bugs::              
 @end menu
 
@@ -417,6 +418,53 @@ The idea behind those mechanisms is that normally all deprecated and
 discouraged features are available, but that you can omit them on
 purpose to check whether your code still relies on them.
 
+@node Manual Conventions
+@section Conventions used in this Manual
+
+We use some conventions in this manual.
+
+@itemize @bullet
+
+@item
+For some procedures, notably type predicates, we use ``iff'' to mean
+``if and only if''.  The construct is usually something like: `Return
+@var{val} iff @var{condition}', where @var{val} is usually
+``@nicode{#t}'' or ``non-@nicode{#f}''.  This typically means that
+@var{val} is returned if @var{condition} holds, and that @samp{#f} is
+returned otherwise.  To clarify: @var{val} will @strong{only} be
+returned when @var{condition} is true.
+@cindex iff
+
+@item
+In examples and procedure descriptions and all other places where the
+evaluation of Scheme expression is shown, we use some notation for
+denoting the output and evaluation results of expressions.
+
+The symbol @samp{@result{}} is used to tell which value is returned by
+an evaluation:
+
+@lisp
+(+ 1 2)
+@result{} 3
+@end lisp
+
+Some procedures produce some output besides returning a value.  This
+is denoted by the symbol @samp{@print{}}.
+
+@lisp
+(begin (display 1) (newline) 'hooray)
+@print{} 1
+@result{} hooray
+@end lisp
+
+As you can see, this code prints @samp{1} (denoted by
+@samp{@print{}}), and returns @code{hooray} (denoted by
+@samp{@result{}}).  Do not confuse the two.
+
+@c Add other conventions here.
+
+@end itemize
+
 @node Reporting Bugs
 @section Reporting Bugs
 

doc/ref/preface.texi

@@ -5,24 +5,11 @@
 @c See the file guile.texi for copying conditions.
 
 @node Preface
-@chapter Preface
+@unnumbered Preface
 
-This manual documents version @value{VERSION} of Guile, GNU's
+This manual describes how to use Guile, GNU's Ubiquitous Intelligent
-Ubiquitous Intelligent Language for Extensions.  It describes how to
+Language for Extensions.  It relates particularly to Guile version
-use Guile in many useful and interesting ways.
+@value{VERSION}.  The manual is divided into the following chapters.
-
-@menu
-* Manual Layout::               
-* Manual Conventions::          
-* Contributors::                
-* Guile License::               
-@end menu
-
-
-@node Manual Layout
-@section Layout of this Manual
-
-The manual is divided into the following chapters.
 
 @table @strong
 @item Chapter 1: Introduction to Guile
@@ -64,56 +51,13 @@ classes, multiple inheritance and generic functions.
 
 @end table
 
-
+@menu
-@node Manual Conventions
+* Contributors::                
-@section Conventions used in this Manual
+* Guile License::               
-
+@end menu
-We use some conventions in this manual.
-
-@itemize @bullet
-
-@item
-For some procedures, notably type predicates, we use ``iff'' to mean
-``if and only if''.  The construct is usually something like: `Return
-@var{val} iff @var{condition}', where @var{val} is usually
-``@nicode{#t}'' or ``non-@nicode{#f}''.  This typically means that
-@var{val} is returned if @var{condition} holds, and that @samp{#f} is
-returned otherwise.  To clarify: @var{val} will @strong{only} be
-returned when @var{condition} is true.
-@cindex iff
-
-@item
-In examples and procedure descriptions and all other places where the
-evaluation of Scheme expression is shown, we use some notation for
-denoting the output and evaluation results of expressions.
-
-The symbol @samp{@result{}} is used to tell which value is returned by
-an evaluation:
-
-@lisp
-(+ 1 2)
-@result{} 3
-@end lisp
-
-Some procedures produce some output besides returning a value.  This
-is denoted by the symbol @samp{@print{}}.
-
-@lisp
-(begin (display 1) (newline) 'hooray)
-@print{} 1
-@result{} hooray
-@end lisp
-
-As you can see, this code prints @samp{1} (denoted by
-@samp{@print{}}), and returns @code{hooray} (denoted by
-@samp{@result{}}).  Do not confuse the two.
-
-@c Add other conventions here.
-
-@end itemize
 
 @node Contributors
-@section Contributors to this Manual
+@unnumberedsec Contributors to this Manual
 
 The Guile reference and tutorial manuals were written and edited
 largely by Mark Galassi and Jim Blandy.  In particular, Jim wrote the
@@ -149,7 +93,7 @@ The chapter on GOOPS was written by Christian Lynbech, Mikael
 Djurfeldt and Neil Jerram.
 
 @node Guile License
-@section The Guile License
+@unnumberedsec The Guile License
 @cindex copying
 @cindex GPL
 @cindex LGPL