Some text characters not showing correctly in "Programmer Art" resource pack

Text characters 'þ', 'Þ', and 'Ð' not displaying correctly in with the in-built Programmer Art resource pack.

What I expected to happen was...:
I thougt the chraacters would display normally.

What actually happened was...:
Instead of the characters displaying normally, it displays very large icons shaped like strange 'x' and 'L's.

Steps to Reproduce:
1. Open a game
2. Switch on the 'Programmer Art' resource pack.
3. Type in any of the characters 'þ', 'Þ', 'ð' in chat or on a sign.