GitLab

There was an error that slipped through and only showed up on PR merge (https://travis-ci.org/google/googletest/jobs/364304396/config ) , we dont want that again

Had an instance where the breakage was not detected until the actual merge. Need to be better than that

Trying to get around mongoDB expired keys, etc

Disable expensive builds on pull requests.

When this build works, we know the autoconf support is working.

This refactored test build scripts to enable
bazel-build scripts in Travis.

... and remove explicit gcc installation (will be installed with g++
automatically)

This turns on optimization which allows the compiler to discover more
problems and omit some more warnings.

While cmake does not complain on build type 'debug', the cmake
documentation always spells it 'Debug', so take this.

There is no need for separate 'googlemock' and 'googletest' builds,
as the 'googlemock' build includes 'googletest' and it's unit tests.