Fix old descriptions of Stow (#22)

De-emphasise the package management aspects, since these days
almost everyone prefers to use modern package managers such as
rpm / dpkg / Nix for (system-wide) package management.

Also include more popular modern use cases for Stow such as management
of dotfiles and software compiled in the user's $HOME directory.

Fixes #22: https://github.com/aspiers/stow/issues/22

bin/stow.in

@@ -1,6 +1,6 @@
 #!@PERL@
 
-# GNU Stow - manage the installation of multiple software packages
+# GNU Stow - manage farms of symbolic links
 # Copyright (C) 1993, 1994, 1995, 1996 by Bob Glickstein
 # Copyright (C) 2000, 2001 Guillaume Morin
 # Copyright (C) 2007 Kahlil Hodgson
@@ -21,7 +21,7 @@
 
 =head1 NAME
 
-stow - software package installation manager
+stow - manage farms of symbolic links
 
 =head1 SYNOPSIS
 
@@ -29,33 +29,34 @@ stow [ options ] package ...
 
 =head1 DESCRIPTION
 
-This manual page describes GNU Stow @VERSION@, a program for managing
-the installation of software packages. This is not the definitive
-documentation for stow; for that, see the info manual.
+This manual page describes GNU Stow @VERSION@.  This is not the
+definitive documentation for Stow; for that, see the accompanying info
+manual, e.g. by typing C<info stow>.
 
-Stow is a tool for managing the installation of multiple software
-packages in the same run-time directory tree. One historical
-difficulty of this task has been the need to administer, upgrade,
-install, and remove files in independent packages without confusing
-them with other files sharing the same filesystem space. For instance,
-it is common to install Perl and Emacs in F</usr/local>.  When one
-does so, one winds up (as of Perl 4.036 and Emacs 19.22) with the
-following files in F</usr/local/man/man1>: F<a2p.1>; F<ctags.1>;
-F<emacs.1>; F<etags.1>; F<h2ph.1>; F<perl.1>; and F<s2p.1>.  Now
-suppose it's time to uninstall Perl. Which man pages get removed?
-Obviously F<perl.1> is one of them, but it should not be the
-administrator's responsibility to memorize the ownership of individual
-files by separate packages.
+Stow is a symlink farm manager which takes distinct sets of software
+and/or data located in separate directories on the filesystem, and
+makes them all appear to be installed in a single directory tree.
 
-The approach used by Stow is to install each package into its own
-tree, then use symbolic links to make it appear as though the files
-are installed in the common tree. Administration can be performed in
-the package's private tree in isolation from clutter from other
-packages.  Stow can then be used to update the symbolic links. The
-structure of each private tree should reflect the desired structure in
-the common tree; i.e. (in the typical case) there should be a F<bin>
-directory containing executables, a F<man/man1> directory containing
-section 1 man pages, and so on.
+Originally Stow was born to address the need to administer, upgrade,
+install, and remove files in independent software packages without
+confusing them with other files sharing the same file system space.
+For instance, many years ago it used to be common to compile programs
+such as Perl and Emacs from source.  By using Stow, F</usr/local/bin>
+could contain symlinks to files within F</usr/local/stow/emacs/bin>,
+F</usr/local/stow/perl/bin> etc., and likewise recursively for any
+other subdirectories such as F<.../share>, F<.../man>, and so on.
+
+While this is useful for keeping track of system-wide and per-user
+installations of software built from source, in more recent times
+software packages are often managed by more sophisticated package
+management software such as rpm, dpkg, and Nix / GNU Guix, or
+language-native package managers such as Ruby's gem, Python's pip,
+Javascript's npm, and so on.
+
+However Stow is still used not only for software package management,
+but also for other purposes, such as facilitating a more controlled
+approach to management of configuration files in the user's home
+directory, especially when coupled with version control systems.
 
 Stow was inspired by Carnegie Mellon's Depot program, but is
 substantially simpler and safer. Whereas Depot required database files
@@ -66,6 +67,9 @@ will never delete any files, directories, or links that appear in a
 Stow directory (e.g., F</usr/local/stow/emacs>), so it's always
 possible to rebuild the target tree (e.g., F</usr/local>).
 
+Stow is implemented as a combination of a Perl script providing a CLI
+interface, and a backend Perl module which does most of the work.
+
 =head1 TERMINOLOGY
 
 A "package" is a related collection of files and directories that