tex-ltxcmds{,-doc}: update to 1.25

Changed the definitions of \ltx at iffilelater, \ltx at ifpackagelater
and \ltx at ifclasslater to support dates in ISO format in same way as the
LaTeX kernel does it since 2017. The commands now use the same test as the
LaTeX kernel. \pdfmatch is no longer used with pdftex, and the tests for
dates before 1994 have been removed

(markd)