[pdftex] review of some paraneters in config file

[The Thanh Han]

Hi,

a few parameters have been added to config file:

pdf12compliantcode
pdf13compliantcode
pdfminorversioncode
alwaysusepdfpageboxcode
pdfoptionpdfinclusionerrorlevel

I wonder whether we have to change a few of them; as 

pdf12compliantcode
pdf13compliantcode

are here, then we probably have to do the same thing for pdf1.4, pdf1.5
and so on. And when we get to pdf2.0, we will have to have something
like pdfmajorversioncode.

So if not too many people are depending on those above features, I am
going to reimplement them. Please let me know your opinions.

Regards,
Thanh