Added brand new (and still experimental) checks for CWEs 415 and 416 together with a new interprocedural data-flow analysis engine written in Rust. Add `-partial=Memory` as command line flag to try out the new checks.

Unit tests no longer fail silently on Travis CI builds.

* Added feature to compiler test cases with more than one compiler. Added clang as first examples. Fixed test cases to work with gcc

* Added acceptance tests for clang x64, adjusted Travis scripts (now
runs also unittests), install_cross_compilers installs also clang.

* Skips test for cwe415, which is broken on clang + Ubuntu 16.04

* Added feature to compiler test cases with more than one compiler. Added clang as first examples. Fixed test cases to work with gcc

* Added acceptance tests for clang x64, adjusted Travis scripts (now
runs also unittests), install_cross_compilers installs also clang.

* Skips test for cwe415, which is broken on clang + Ubuntu 16.04

* Added change to CHANGES.md

* Fixed test issue: test for json output was pre-compiler suffix.

This builds cwe_checker and runs the test suite on Travis CI.