These patches try to improve our Travis CI usage (few failures the last days):
- lower false negative rate (mostly network issues),
- improved code coverage,
- speedup failure detection.

dropped since v2 (will follow as a separate series)
- multicore parallelism use
- cache use

Patch 1 is expected to enter /master as of yesterday.
Travis warned few months ago:
  "On Wednesday, June 21st 2017, we are going to update all our Ubuntu Trusty
  14.04 images."

Patches 4-6 try to avoid aborting a job on network failure.

Patches 7-9 intend to speedup jobs.

Patch 10 gives hint when ./configure fails, patch 12 silent build warnings.

RFC patch 13 uses upgraded GCC v5 -> v6.
RFC patch 14 don't fails the build if the slow gprof/gcov job fail.

Patches 15, 16 add more OSX VMs/toolchains (older, newer, bleeding edge).

Regards,

Phil.

Peter Maydell (1):
  travis: install more library dependencies

Philippe Mathieu-Daudé (15):
  travis: update sudo-enabled Trusty images
  travis: enable multiple caching features
  travis: increase S3 cache timeout
  travis: retry if llvm.org timeouts
  travis: retry when git submodules initialization fails
  travis: split the gprof/gcov job
  travis: reorder matrix to speedup failure
  travis: reduce git clone depth
  travis: check ./configure outcome, dump config.log on failure
  travis/osx: use readable YAML
  travis/osx: silent texinfo warnings
  RFC travis: use gcc-6 sanitizers
  RFC travis: allow_failures for gprof/gcov
  RFC travis/osx: build using more Xcode versions
  NOTFORMERGE travis/osx: build using bleeding Xcode

 .travis.yml | 134 +++++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 97 insertions(+), 37 deletions(-)

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2.13.3