Add paper to printers

SimH printers have been somewhat boring.  More importantly, they have been rather less than realistic and their primary product - printed paper has not been simulated.

Further, so-called 'modern improvements' have made it difficult to render the ASCII output files of SimH printers faithfully on "modern" systems.

This edit provides two new capabilities to SimH:

o lpt2pdf - a utility that will take an ASCII file and render it on simulated paper in a .PDF file

o The callable API for printer emulators to write PDF directly (while still being able to write ASCII text if desired.)

The first two sample printers: pdp10_lp20 and pdp11_lp provide this capability for the pdp11, VAX and pdp10 products.

Enabling it in other emulated systems does not require much work.

The technical and user details are in lpt2pdf.h.

The user details are in simh_doc.doc.

This edit does not include the Makefile/Projectfile support, hopefully to be provided by Mark P.
Minor build errors on linux