Implements a command that can take a list of directions and numbers, and
make the player move through it. ( example: "swalk 2se2sen" ). Since it
adds the directional commands to the player's input buffer, it runs like
if the player really entered those directions, so movement lag still
occurs, aggr mobs can still attack, etc.

You'll have to change 2 files:
   merc.h (1) and interp.c (2)
Here are the step-by-step instructions:
 * Add lines that start with ++
 * Remove lines that start with --
 * Lines with ... mean that some more code is probably there

**********************************************************************
1) ** in MERC.H                                                      *
**********************************************************************
1.1) add the command function declaration:
++ DECLARE_DO_FUN( do_swalk        ); 

**********************************************************************
2) ** INTERP.C                                                       *
**********************************************************************
2.1) Add the "swalk" command to the command function:
++ { "swalk",         do_swalk,      POS_STANDING, 0, LOG_NORMAL, 1 }

2.2) Add the contents of the swalk.c file to interp.c
eg, on a unix/linux shell type:
   cat swalk.c >> interp.c