travis-ci: split matrix into "cron" and "push" (move less popular builds to cron)

[Илья Шипицин]

hello,

I played a bit with "if" condition

https://github.com/chipitsine/haproxy/blob/master/.travis.yml

in short, we can specify condition like that

  - os: osx
    if: type == cron
    compiler: clang
    env: TARGET=osx FLAGS="USE_OPENSSL=1" OPENSSL_VERSION=1.1.1c

full list of conditions: https://docs.travis-ci.com/user/conditions-v1

so, I suggest to

a) osx goes to "cron only"
b) cygwin goes to "cron only"
c) boringssl goes to "cron only"
d) libressl goes to "cron only"
e) openssl-1.1.0, 1.0.2 go to "cron only"

also, someone with admin rights have to add "cron" jobs to travis-ci (it is
done via web interface only)


any suggestion ?

Ilya Shipitsin