man: Use -w instead of --path

--path is an alias command line option for -w.
It is available since man-db 2.6.1-pre1 (2012-02-05).

See commit:
http://git.savannah.gnu.org/cgit/man-db.git/commit/?id=e37bc92f352c97c61ef63de745e43574d27b1276

For portability (like man-1.6g), prefer using original -w switch.

Signed-off-by: Matthieu Crapet <mcrapet@gmail.com>

completions/man

@@ -58,7 +58,7 @@ _man()
 
     local manpath
     if [[ $OSTYPE == *@(darwin|linux|freebsd|cygwin)* ]] || _userland GNU; then
-        manpath=$( manpath 2>/dev/null || command man --path )
+        manpath=$( manpath 2>/dev/null || command man -w )
     else
         manpath=$MANPATH
     fi