AST: Fixed detection of operator new/delete - don't hang when C code is checked as C++ (#5910)
SymbolDatabase: 'const' can't be the name of a variable - fix use after free #5882
avr.cfg: Added support for more functions.
Speedup checking large amounts of arrays (#5615) by avoiding Token::Match calls in CheckBufferOverrun::checkScope(2).
-> Decreased entire checking time on a subset of the attached file by 66% (MSVC12, x64, non-matchcompiled)
Refactorizations optimizing std::string usage:
1) Added global static const std::string emptyString; object:
-> Replaces some static variables in functions which might be not threadsafe
-> Avoids constructor call (std::string::string(""))
-> Even functions that return an empty string in some branches can return by reference now.
Added to config.h to ensure that it is available everywhere

2) Added overloads for TestFixture::assertEquals for the most common use cases:
-> Moves conversion from const char[] to std::string into a function, reducing code duplication in binary.
Store Token::_originalName on heap, since it is only used for a small amount of Tokens (reduce memory usage of TokenList by ~12% (x64))
avr.cfg and posix.cfg: Added support for more functions.
AST: fixed ast for '++i;'
CheckBufferOverrun: Added bufferOverrun2 that is based on ValueFlow/SymbolDatabase/Ast from the start. Replaced some old checking.
Fix some compiler warnings
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.