MS-DOS: Add Extended2 symbols to the bundled fonts

This change adds U+2299, U+2601 and U+2980 to the bundled fonts, so
that all symbols specified in the Extended2 symbol set are available.

Also, a few more directives are added to the files, so that FontForge
can load them and display their contents.

sys/msdos/fonts/nh-u24b.bdf

@@ -1,12 +1,21 @@
 STARTFONT 2.1
 FONTBOUNDINGBOX 12 24
-STARTPROPERTIES 3
+STARTPROPERTIES 8
 NOTICE "Additional characters to use with ter-u24b.bdf"
-COPYRIGHT "Copyright 2022 Ray Chason."
+COPYRIGHT "Copyright 2022, 2026 Ray Chason."
+NOTICE "Cloud glyph adapted from the uw-ptty0 font at"
+NOTICE "https://people.mpi-inf.mpg.de/~uwe/misc/uw-ttyp0/"
 NOTICE "NetHack may be freely redistributed.  See license for details."
+PIXEL_SIZE 24
+CHARSET_REGISTRY "ISO10646"
+CHARSET_ENCODING "1"
 ENDPROPERTIES
+CHARS 6
 STARTCHAR tripletilde
 ENCODING 8779
+SWIDTH 500 0
+DWIDTH 12 0
+BBX 12 24 0 -5
 BITMAP
 0000
 0000
@@ -33,8 +42,42 @@ BITMAP
 0000
 0000
 ENDCHAR
+STARTCHAR uni2299
+ENCODING 8857
+SWIDTH 500 0
+DWIDTH 12 0
+BBX 12 24 0 -5
+BITMAP
+0000
+0000
+0000
+0000
+0000
+0000
+0F00
+3FC0
+70E0
+6060
+C030
+C630
+C630
+C030
+6060
+70E0
+3FC0
+0F00
+0000
+0000
+0000
+0000
+0000
+0000
+ENDCHAR
 STARTCHAR uppereighth
 ENCODING 9620
+SWIDTH 500 0
+DWIDTH 12 0
+BBX 12 24 0 -5
 BITMAP
 FFF0
 FFF0
@@ -63,6 +106,9 @@ FFF0
 ENDCHAR
 STARTCHAR righteighth
 ENCODING 9621
+SWIDTH 500 0
+DWIDTH 12 0
+BBX 12 24 0 -5
 BITMAP
 0030
 0030
@@ -89,4 +135,66 @@ BITMAP
 0030
 0030
 ENDCHAR
+STARTCHAR uni2601
+ENCODING 9729
+SWIDTH 500 0
+DWIDTH 12 0
+BBX 12 24 0 -5
+BITMAP
+0000
+0000
+0000
+0000
+0000
+0000
+0000
+0000
+03C0
+07E0
+0E60
+3C60
+7060
+6060
+7FC0
+3F80
+0000
+0000
+0000
+0000
+0000
+0000
+0000
+0000
+ENDCHAR
+STARTCHAR uni2980
+ENCODING 10624
+SWIDTH 500 0
+DWIDTH 12 0
+BBX 12 24 0 -5
+BITMAP
+0000
+0000
+0000
+0000
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+6660
+0000
+0000
+0000
+0000
+0000
+ENDCHAR
 ENDFONT