add command line option --showpaths

Add
	--showpaths
early option to show where NetHack is expecting to find certain files
without starting up a game. It exits afterwards.

Windows sample (for illustration only, locations may differ for you):
    Variable playground locations:
        [hackdir   ]="C:\Users\JohnDoe\NetHack\3.6\"
        [leveldir  ]="C:\Users\JohnDoe\AppData\Local\NetHack\3.6\"
        [savedir   ]="C:\Users\JohnDoe\AppData\Local\NetHack\3.6\"
        [bonesdir  ]="C:\ProgramData\NetHack\3.6\"
        [datadir   ]="C:\personal\nhdev\363\test\binary\"
        [scoredir  ]="C:\ProgramData\NetHack\3.6\"
        [lockdir   ]="C:\ProgramData\NetHack\3.6\"
        [sysconfdir]="C:\ProgramData\NetHack\3.6\"
        [configdir ]="C:\Users\JohnDoe\NetHack\3.6\"
        [troubledir]="C:\Users\JohnDoe\NetHack\3.6\"
    Your system configuration file (in sysconfdir):
        "C:\Users\JohnDoe\NetHack\3.6\sysconf"
    Your system symbols file (in sysconfdir):
        "C:\Users\JohnDoe\NetHack\3.6\symbols"
    Your personal configuration file (in configdir):
        "C:\Users\JohnDoe\NetHack\3.6\.nethackrc"

Linux (for illustration only, locations may differ for you):
    Your system configuration file:
        "/home/johndoe/nh/install/games/lib/nethackdir/sysconf"
    Your system symbols file:
        "/home/johndoe/nh/install/games/lib/nethackdir/symbols"
    Your personal configuration file:
        "/home/johndoe/.nethackrc"

doc/nethack.6

@@ -47,6 +47,9 @@ nethack \- Exploring The Mazes of Menace
 .B \-ibm
 ]
 [
+.BR \-\-showpaths
+]
+[
 .BR \-\-version [ :paste ]
 ]
 .PP
@@ -223,6 +226,10 @@ the list of top scorers, and a subdirectory
 .I save
 where games are saved.
 .PP
+.B \-\-showpaths
+can be used to cause NetHack to show where it is expecting
+to find various configuration files.
+.PP
 .B \-\-version
 can be used to cause NetHack to show the version information it
 was compiled with, then exit. That will include the