groveller: fix to work with new type syntax

Use C-WRITE instead of C-PRINT-SYMBOL when emitting types to deal with
the fact that some types are more than just one symbol now.

e.g. 'foo vs '(:struct foo) and '(:pointer (:struct foo))

Fixes: Bug 1065432
Merge branch 'master' of git://github.com/cffi/cffi