[pdftex] Deprecated page ProcSet arrays

[Karl Berry]

Thanh implemented a new primitive parameter; it's in the TL (and pdftex)
sources now. I'll add it to the pdftex manual as usual before the release.

\pdfomitprocset values:
- If zero (default), omit outputting /ProcSet if writing PDF 2.0
  (\pdfmajorversion >=2), but include it otherwise.
- If >0, omit /ProcSet unconditionally.
- If <0, include /ProcSet unconditionally.

Hope that suits. --thanks, karl.