Merge branch 'travis-ci-os-matrix-v2'

Merge branch 'travis-ci-os-matrix-v2'

This increases libevent coverage to:
- os:osx

- cmake -DEVENT__DISABLE_MM_REPLACEMENT=ON
- cmake -DEVENT__ENABLE_VERBOSE_DEBUG=ON
- configure --disable-openssl
- configure --disable-thread-support
- configure --disable-malloc-replacement

- fix travis-ci builds under automake >1.11

Possible failures after this patch set (not always, IOW in some builds this
issues aren't real issues):
- some failures but mostly because of timing issues, must be fixed separately.
- https://travis-ci.org/azat/libevent/jobs/129430229 # on brew update
- https://travis-ci.org/azat/libevent/jobs/129430221 # some locking issues

* travis-ci-os-matrix-v2:
  automake: define serial-tests only if automake have this option
  test/automake: don't use paralell test harness (since automake 1.12)
  travis-ci/osx: relink gcc/g++ instead of clang
  travis-ci: enable multi-os mode (osx, linux)
  travis-ci: increase matrix (--disable-foo)
  travis-ci: adjust alignment

Fixes: #356
Travis-CI: https://travis-ci.org/azat/libevent/builds/129430181