* .travis.sh: Rewrite for clarity and speed. Testing shows that valgrind
and ASan don't play well together. So split their executions.
* .travis.yml: Enable ccache for builds. Also try to update libc6 if
possible
* .travis.yml: Do not run on OSX with CC=gcc. This is because on OSX,
gcc is only a wrapper around clang.
* .travis_setup.sh: Cosmetic changes only
* Makefile.am (check-coverage): Explcicitly disable valgrind tests when
checking coverage
* tests/libtest.c (wget_test): Use a provided suppressions file for
valgrind. This is required since the valgrind version on Travis seems to
be out of sync with libc. This causes valgrind to report a memory bug
falsely.
* tests/valgrind-suppressions: New file with some valgrind suppressions.
Included suppressions are for a valgrind/libc bug and to suppress
reachable memory messages from within gnutls