Log Message:
texlive: update to 2020

General:
* The \input primitive in all TeX engines, including tex, now also accepts a
  group-delimited filename argument, as a system-dependent extension. The usage
  with a standard space/token-delimited filename is completely unchanged. The
  group-delimited argument was previously implemented in LuaTeX; now it is available
  in all engines. ASCII double quote characters (") are removed from the \ 
filename,
  but it is otherwise left unchanged after tokenization. This does not currently
  affect LaTeX’s \input command, as that is a macro redefinition of the standard
  \input primitive.
* New option –cnf-line for kpsewhich, tex, mf, and all other engines, to support
  arbitrary configuration settings on the command line.
* The addition of various primitives to various engines in this and previous years
  is intended to result in a common set of functionality available across
  all engines.

epTeX, eupTeX: New primitives \Uchar, \Ucharcat, \current(x)spacingmode, \ifincsname;
 revise \fontchar?? and \iffontchar. For eupTeX only: \currentcjktoken.

LuaTeX: Integration with HarfBuzz library, available as new engines luahbtex
 (used for lualatex) and luajithbtex. New primitives: \eTeXgluestretchorder,
 \eTeXglueshrinkorder.

pdfTeX: New primitive \pdfmajorversion; this merely changes the version number
 in the PDF output; it has no effect on any PDF content. \pdfximage and similar
 now search for image files in the same way as \openin.

pTeX: New primitives \ifjfont, \iftfont. Also in epTeX, upTeX, eupTeX.

XeTeX: Fixes for \Umathchardef, \XeTeXinterchartoks, \pdfsavepos.

Dvips: Output encodings for bitmap fonts, for better copy/paste capabilities.