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)

sys/unix/hints/macOS.370

@@ -27,7 +27,7 @@ ifeq ($(MAKELEVEL),0)
 PRECHECK+=checkmakefiles
 # all files included from this hints file get listed
 # in HINTSINCLNAMES (without suffix and without a path)
-HINTSINCLNAMES := compiler cross-pre cross-post \
+HINTSINCLNAMES := compiler cross-pre1 cross-pre2 cross-post \
 		gbdates-pre gbdates-post \
 		multiw-1 multiw-2 misc \
 		multisnd1-pre multisnd2-pre multisnd-post
@@ -55,6 +55,8 @@ endif
 # you're reading this in Makefile augmented by hints, that may not be true).
 #
 
+#-INCLUDE cross-pre1.370
+
 #-INCLUDE multiw-2.370
 
 # compiler.370 contains compiler detection and adjustments common
@@ -427,7 +429,7 @@ SYSCONFENSURE = (if ! test -f $(INSTDIR)/sysconf ; then \
 # Install.Qt mentions a patch for macos - it's not there (it seems to be in the Qt binary
 # package under the docs directory).
 #
-#-INCLUDE cross-pre.370
+#-INCLUDE cross-pre2.370
 #
 #
 #-INCLUDE gbdates-pre.370