doc: updated man pages for many tools

This patch perform simple fixes to the man pages and tool help page:
 - minor style updates, to get cleaner pages
 - option re-ordering, to have them in alphabetic order (easier to search for)
 - consistency updates for descriptions and number of dash
 - spell-checking

The biggest changes are:
 - wmagnify: the option 'vdisplay' was not documented at all;

 - getstyle: the list of attributes that are taken for the Style are now
described in their own section to clarify the page;

 - setstyle: the help page left thinking that the file argument was
optional, which is not the case;

 - wdread: as the Exit Code may be useful, and it is not unusable, it is
now documented;

 - wmgenmenu: added information about how the content of the menu is
generated;

 - wmsetbg: added a section about dithering/best-match because as nowadays
most screens are in True Color, the reason for the option may not be clear.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

doc/WPrefs.1x

@@ -1,9 +1,9 @@
-.TH "Window Maker" 1x "March 2001" "Debian Project"
+.TH WPrefs 1x "March 2001"
 .SH NAME
 WPrefs \- Window Maker configuration tool
 .SH SYNOPSIS
 .B WPrefs
-.I "[-options]"
+.RI [ options ]
 .SH "DESCRIPTION"
 WPrefs.app is the preferences "editor" for the WindowMaker window manager. It
 can be used to set most of the preference options of WindowMaker and define
@@ -18,14 +18,14 @@ of WindowMaker that are not related to configuration.
 system-wide configuration file is saved.\fP
 .SH "OPTIONS"
 .TP
-.B \-display host:display.screen
+.BI \-display " host:display.screen"
 specify display to use.
 .TP
-.B \-\-version
-display version number and exit
-.TP
 .B \-\-help
-display help message and exit
+print a help message with the list of options
+.TP
+.B \-\-version
+print the version of Window Maker from which the program comes
 .SH FILES
 .TP
 .B ~/GNUstep/Defaults/WindowMaker