split some code into separate files

new .h files: hacklib.h selvar.h stairs.h

new .c files: calendar.c, getpos.c, report.c, selvar.c, stairs.c,
              strutil.c, wizcmds.c

cleanup of hacklib.c and mdlib.c

hacklib contains functions that do not have to link with the core

relocate wiz commands from cmd.c to wizcmds.c

relocate CRASHREPORT stuff to report.c

relocate getpos stuff from do_name.c to getpos.c

remove temporary struct definition from extern.h

cross-compile PRE-section split into cross-pre1.370 and cross-pre2.370

Windows sys/windows/Makefile.nmake and sys/windows/Makefile.mingw32 and
visual studio project file updates

Unix sys/unix/Makefile.src, sys/unix/Makefile.utl

populate selvar.c and selvar.h

build on MS-DOS (not cross-compile) Makefile updates
for sys/msdos/Makefile.GCC (untested)

vms updates for above (untested)

include/dungeon.h

@@ -31,15 +31,6 @@ typedef struct s_level { /* special dungeon level element */
     d_flags flags;  /* type flags */
 } s_level;
 
-typedef struct stairway { /* basic stairway identifier */
-    coordxy sx, sy;         /* x / y location of the stair */
-    d_level tolev;        /* where does it go */
-    boolean up;           /* up or down? */
-    boolean isladder;     /* ladder or stairway? */
-    boolean u_traversed;  /* hero has traversed this stair */
-    struct stairway *next;
-} stairway;
-
 /* level region types */
 enum level_region_types {
     LR_DOWNSTAIR = 0,