This commit extends the Travis CI configuration to build HAProxy
with gcc on Linux, clang on Mac and cleans up the build flag
configuration to be easier extendable.
Note: At the moment HAProxy fails on Travis for configurations
on OS X
currently only xenial/clang build is enabled. osx and xenial/gcc
will be enabled later.
travis-ci is cloud based continuous integration, builds will be
started automatically if they are enabled for certain repo or fork.
Signed-off-by: Ilya Shipitsin <chipitsine@gmail.com>
