Description :

With new HD font support, we can change these files :

/font/alternate.png
/font/default.png
/font/glyph_00.png
...
/font/glyph_FF.png

But we can't change :

/font/glyph_sizes.bin

Since this file is related to unicode glyph size I think it must be possible to change it.
When forcing the use of a custom glyph_sizes.bin file, the default font is dysfunctional.

Testing protocol :

1. Download a fresh Minecraft 13w09a/b
2. Download and install as a texture pack the zip file below
3. Start Minecraft
4. Set "Native Unicode" as your texture pack
5. Set "French" as your language (it need unicode for somes silly things likes "...")

   You should have the same result as Fail.png

6. Close Your Minecraft
7. Put the content of the texture pack into bin/Minecraft.jar and delete META-INF
8. Restart your Minecraft

   You should have the same result as Good.png
   Text is misplaced on buttons, but depend of another bug report.

9. Set "English (UK)" as your language (it don't need unicode and return to default)

   You should have the same result as Fail2.png