travis: change build optimization level back to -O2 (from -O3) as discussed in
https://github.com/danmar/cppcheck/commit/59077b06f9be2597db57753a27aff93ee294a670
Merge pull request #344 from matthiaskrgr/travis_O

travis: change build optimization level back to -O2 (from -O3) as discussed
Refactoring: Move isScopeNoReturn implementation to library and reuse it both in ValueFlow and Tokenizer
Astyle run; Extended std.cfg and avr.cfg about a few more functions.
Extended std.cfg and avr.cfg about more functions.
std.cfg: Added support for bsearch.
Fixed #5923 (false positive: (error) Resource leak: fp (static file pointer))
Improved performance of CheckBufferOverrun::checkScope() (#5944):
-> Speedup by 40% (MSVC12, x64, not matchcompiled) on the file attached to the ticket
travis: replace kernel check with clang check.

Check clang instead of kernel, which is a lot faster.
Make clang check failure fatal to the build.
travis: add -DCHECK_INTERNAL to the VERIFY=1 job to automatically fetch issues like #5869 via travis, check clang with --exception-handling
travis: make clang check sensitive to internal cppcheck errors.