Re-add chars 0x00 - 0x1F to the font

- Some levels used chars < 0x20 as non-collapsible spaces, those would
  now show up as [?]
- I recently found out how making characters < 0x20 6 pixels wide
  doesn't work if they're missing from the font altogether

Therefore, the font now starts at 0x00 again instead of 0x20, like it
used to.

Arguably it was an advantage that the game would look extremely messed
up if you made a mistake with the fonts. In particular, a common
mistake could be to copy the new Unicode font.png, but forget to copy
the corresponding font.txt. However, 2.3 didn't come with the unicode
font, 2.4 will, so it'll be a lot less common for people to need to
manually copy the font. And if they do, it's probably for their own
level, and they have something in mind for the font, and if it doesn't
work they'll know fast enough when whatever they're planning doesn't
work (and it would only affect their own level's text, not any menus).

desktop_version/fonts/font.fontmeta

@@ -5,7 +5,7 @@
     <height>8</height>
     <white_teeth>1</white_teeth>
     <chars>
-        <range start="0x20" end="0x7F"/>
+        <range start="0x00" end="0x7F"/>
         <range start="0xA0" end="0x17F"/>
         <range start="0x18F" end="0x18F"/>
         <range start="0x218" end="0x21B"/>