It works pretty fine.
So, I think, it's time to move it from testing.

adds a checkpath to initd for /usr/lib/exim
this stops hourly messages in exim's mainlog:

'Couldn't open /usr/lib/exim/: not loading lookup modules'

* checkpath added to initd so exim starts
* crypteq added for hashed password support in flat files

The package on current version (4.88) FTBFS due to URL returning 404.
It seems that the URL scheme just works for the latest version.

Bumping to the latest version 4.89.

The checksum of the package also matches the version released:
https://lists.exim.org/lurker/message/20170307.215703.bc9b50b4.en.html

Adds exim-gencert from Debian altered to use custom expiry date
and key size (3 years / 4096 bit by default).

Review notes:
Cleaned the exim.gencert script. ~ @jirutka

Something about the gcc invocation was causing it to not link libpq or
libmysql so the exim-postgresql and exim-mysql packages were unusable at
runtime.

linux-headers build-time deb didn't seem to cause any problems, but it
issued a warning about linux/ip.h not found, and we can fix that easily
enough so we should.

Fixes #6775

And cosmetic fixes in init-script and APKBUILD.