ps: exploit the simplified library interface for wchan

This patch was made necessary by those library changes
in support of recently revised/simplified wchan logic.

In addition, this commit eliminates a broken alternate
'namelist' provision which was intended to allow users
to specify a System.map file to be used in translating
addresses into function names. But, the real effect of
the now defunct 'N' and '-n' options was to indirectly
force addresses (not names) to be displayed since such
user named map files could not be successfully parsed.

Besides when the required FRAME_POINTER kconfig option
is absent there is no address to translate and when it
is present /proc/PID/wchan is already translated. Thus
an alternate mapping is unnecessary and inappropriate.

[ we'll forgive POSIX for documenting '-n  namelist' ]

Reference(s):
http://www.freelists.org/post/procps/WCHAN,11

Signed-off-by: Jim Warner <james.warner@comcast.net>

ps/common.h

@@ -294,7 +294,6 @@ extern int             header_type; /* none, single, multi... */
 extern int             include_dead_children;
 extern int             lines_to_next_header;
 extern int             max_line_width;
-extern const char     *namelist_file;
 extern int             negate_selection;
 extern int             page_size;  // "int" for math reasons?
 extern unsigned        personality;