Log Message:
mupdf: Update to 1.20.0

Changes:
1.20.0
------
Experimental C# bindings.
Cross compilation should no longer need a host compiler.
Major additions to JNI bindings.

New API to edit outline
New API to resolve and create links
New API to toggle individual layers in PDF
   Layer panel in mupdf-gl
   Layer option in mutool draw
New API to add a Javascript console
   Console panel in mupdf-gl

Text search API extended to be able to distinguish between separate
search hits.

Command line tool improvements:
   all: Negative page numbers to index from the last page
   mutool draw: Add option to render document without text
   mutool draw and convert: Support DPI option in text and HTML output

New hybrid HTML output format using "scripts/pdftohtml" script:
   Graphics in a background image
   Text on top

Improved WASM viewer demo
   Support high DPI screens
   Progressive loading

Update to zlib 1.2.12 for security fix.