tiles-related build stuff

* Add missing entry for include/tile.h to (top)/Files; also
  add new entry for generated file util/tiletxt.c (Unix only);
* Add several missing entries for tile utility programs that
  can be built by sys/unix/Makefile.utl to util/.gitignore;
* Update sys/unix/Makefile.utl to build 'tilemap' differently so
  that it won't leave behind an unwanted subdirectory tree under OSX:
    util/tilemap.dSYM/
    util/tilemap.dSYM/Contents/
    util/tilemap.dSYM/Contents/Info.plist
    util/tilemap.dSYM/Contents/Resources/
    util/tilemap.dSYM/Contents/Resources/DWARF/
    util/tilemap.dSYM/Contents/Resources/DWARF/tilemap
  It now generates util/tiletxt.c on the fly, to be compiled into
  tiletxt.o, so that tilemap.c can be compiled in the ordinary
  manner and tilemap.o can be kept around for dependency checking.
  (Creating real source file win/share/tiletxt.c would be a little
  bit cleaner, but it's effectively two lines long so seems silly
  to be in the source distribution.)  I looked to see whether I
  could find a linker or compiler option to suppress that stuff but
  failed.  I'm sure something of the sort must exist but didn't
  pursue it.  Someday I might actually learn about how OSX works....

util/.gitignore

@@ -1,13 +1,19 @@
-dgn_yacc.c
 dgn_lex.c
-makedefs
-tilemap
-dgn_comp
+dgn_yacc.c
 lev_lex.c
 lev_yacc.c
-tile2x11
+tiletxt.c
+makedefs
+dgn_comp
 lev_comp
-tileedit
-tile2bmp
 dlb
 recover
+tilemap
+tileedit
+tile2x11
+tile2bmp
+tile2beos
+gif2txt
+txt2ppm
+tile2img.ttp
+xpm2ppm.ttp