Do not directly throw from within tl_assert() if dialect is >=C++11

[Peter-Levine]

Building with >=C++11 (e.g., GCC-6), throwing an uncaught exception from within a destructor is generally considered dangerous and, when -Werror=terminate is forced in CXXFLAGS (as can be with Gentoo Linux, see bug 612978) it will break the compile. tl_assert() macro is expanded in some destructors (e.g., Child::~Child() from "src/unit_tests/tlXMLParser.cc"). Since function attribute [[noreturn]] is defined for >=C++11, better to use that instead of throw int(0).

[Peter-Levine]

@klayoutmatthias

Thanks for pointing that out. I found a somewhat different solution here: http://stackoverflow.com/questions/39543449/how-to-use-noreturn-attribute-in-c

From the thread:

If you are stuck with pre-C++11 compilers, you can wrap up a simple macro that uses built-in compiler attributes in a hopefully portable way:

AFAIK, __attribute__((noreturn)) is a GNU C extension and is not portable.

Standards proposal with some relevant info on noreturn portability.