Quickbook: Fix issue with mixed version templates.
If a 1.5 template called a 1.4 template, its parent would be its
'dynamic' parent (the 1.5 template), whose parent would be its lexical
parent - breaking the dynamic lookup. I've changed it so that when
using a dynamic lookup, 1.5+ templates are skipped over. That means
they can use whatever variable names they wish without issues.
It does mean that if a 1.4- template was specifically written to use
dynamic lookup, then it wouldn't be callable from 1.5. So it might
be better if they didn't skip over 1.5+ templates.
Alternatively if might be better to always lexical scoping, even for
older versions, on the assumption that it was a bug.
