[pdf-devel] opaque pointers

[jemarch]

I just committed support for opaque pointers into the trunk.

Some notes:

 - The modules pdf-types, pdf-list and pdf-hash maintain the
   structures in the public headers for performance reasons (i.e. to
   allow the client to allocate data in the stack).

 - The modules pdf-time, pdf-stm, pdf-text and pdf-crypt has been
   adapted to include opaque pointers in the public header.

 - A lot of unit tests of pdf-text are dereferencing pdf_text_t
   pointers. I deactivated the tests: now they are compiling but
   failing. I created a new task to fix this problem.

And that is all.