Bump Emacs version to 26.2

* README:
* configure.ac:
* msdos/sed2v2.inp:
* nt/README.W32: Bump Emacs version to 26.2.
1 job for emacs-26 in 25 minutes and 57 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #1313
test

00:25:57