Log Message:
Pull in patch from upstream to fix a build failure under MacOS X.

Fix unexec failure on macOS 10.15.4
* src/unexmacosx.c (unexec_regions_merge): Align region start addresses to
page boundaries and then merge regions.

http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=888ffd960c06d56a409a7ff15b1d930d25c56089

Bump PKGREVISION of emacs26 and emacs26-nox11.