Previously, some errors in Catch configuration would cause exceptions to
be thrown before main was even entered. This leads to call to
`std::terminate`, which is not a particularly nice way of ending the
binary.
Now these exceptions are registered with a global collector and used
once Catch enters main. They can also be optionally ignored, if user
supplies his own main and opts not to check them (or ignored them
intentionally).
Closes#921
* Empty strings are now direct constructed as `std::string()`, not as empty string literals.
* `startsWith` and `endsWith` no longer construct new a string. This should be an improvement
for libstdc++ when using older standards, as it doesn't use SSO but COW and thus even short
strings are expensive to first create.
* Various places now use char literal instead of string literals containing single char.
** `startsWith` and `endsWith` now also have overload that takes single char.
Generally the performance improvements under VS2015 are small, as going from short string
to char is mostly meaningless because of SSO (Catch doesn't push string handling that hard)
and previous commit removed most string handling if tests pass, which is the expect case.
Martin Hořeňovský