op: recognize more glyph names.

PDF allows fonts to override their base encoding, using named glpyhs. This commit adds, among others, the decimal digits, uppercase and lowercase letters, and some greek symbols. It also fixes the validation check for appending a bullet (•) to check against strlen(
op: correctly initialize GSactive.

The graphics state can be pushed and popped. As such, in addition to the stack of the state, a pointer to the active state is kept at all times. While pushing and popping correctly updated the pointer, we were not previously initializing it on startup. While some PDFs - notably, ps2pdf output - worked without issues, other PDFs, which use the graphics state immediately, did not.

This commit resolves that issue by initializing GSactive to the initial graphics state when setting up the renderer.
add pdf2txt rc script
Significantly improved text output
[parsing] fix unexpected report for n
[ops] add Tj
ascii85: support z, validate each character, do NOT change the input buffer
convert image streams to plan 9 Memimage
xref: missed a newline on error printing
add page number finder
ccittfax: use malloc since memmoving directly after
stream: close the filter after use
mkfile: add "deps" rule to install 3rd party stuff
ignore BDC / EMC marked-content operators
fix empty page handling
buffered pagerender