editors/emacs-devel: Update to 2020-06-01 commit c59e878 and...

..remove a local patch that fixed a build issue on systems using version 10
of clang. This version of clang enforces stricter requirements for the
placement of FALLTHROUGH labels. Upstream committed a change that fixes
the build and silences the FALLTHROUGH warning.

https://github.com/emacs-mirror/emacs/commit/e021c2dc2279e0fd3a5331f9ea661e4d39c2e840