PDF: Remove LPI escape sequence

It's easier to handle as a pdf_reopen (which is what would have happened internally anyhow.).
PDF: Deal with leading spaces in parameter strings

When a  parameter string is generated by devices, it's easier to generate leading spaces than to avoid them.

Skip them when parsing the strings.
VAX: LPT VFU support, VAX & PDP-11: LPI support for PDF

The LP11 supports DAVFUs on LP27 and LP29 printers on VAXes.

Requires "Vertical Forms Printing for VMS" layered product.

Implement LPI as a PDF default and newform().

Correct read of LPT buffer - spec'd to return 0s, not last char written.
PDP10: LP20 updates

Add tech notes to show models.

Respect drum character set.

Handle ptich as a parameter.

Don't send LFs on SETTOF; just align the VFU.
PDF: Charset support part 1

Support escape sequences to map printer output to alternate character sets in order to support international drums/chains.

Use ANSI code extension mechanism; include popular language character sets.  (Not all will glyphs will image until a Unicode font can be embedded.)

Default is ASCII + ISO Latin-1.

Properly map ASCII to PDFDoc encodings (via Unicode so eventually a Unicode font can be supported.)

Check LPTPDF major version when appending to protect against future changes.
PDF: Add lpt2pdf and PDFWatcher project files