Further realpath() changes
Merge branch 'davidk'
Fix for Mantis bug 1131: Unicode source (-Cu) fails in Z-code

Turns out to be a one-line fix.

Test case for this:
https://github.com/erkyrath/glk-dev/blob/master/unittests/unisourcetestb.inf

I also re-tested unisourcetest.inf, chinesedicttest.inf, and unidicttest.inf
to make sure this fix doesn't break anything.