Finally did something about the macros regarding systems that have 64
bit support. To be honest I don't like much the result. In the sense
that macros can be helpful sometimes, but also terribly messy and
tricky (e.g. not so fantastic regarding error support). In this case,
I think it doesn't really solve the issue of transparent 64 bit
support for the client regarding the pdf_i64 functions. If the pdf_i64
functions aren't going to be used much through out the code (e.g. time
module), I find it better to go back to the original suggestion by
jemarch and make the support directly on the code using the functions.