Add support for -fno-exceptions (or equivalent)

This means

* Adding new configuration toggle `CATCH_CONFIG_DISABLE_EXCEPTIONS`
and a best-guess configuration auto-checking for it.
* Adding new set of internal macros, `CATCH_TRY`, `CATCH_CATCH_ALL`
and `CATCH_CATCH_ANON` that can be used in place of regular `try`,
`catch(...)` and `catch(T const&)` respectively, while disappearing
when `CATCH_CONFIG_DISABLE_EXCEPTIONS` is enabled.
* Replacing all uses of `throw` with calls to `Catch::throw_exception`
customization point.
* Providing a default implementation for the above customization point
when `CATCH_CONFIG_DISABLE_EXCEPTIONS` is set.
* Letting users override this implementation with their own.
* Some minor changes and ifdefs all around to support the above

projects/CMakeLists.txt

@@ -173,6 +173,7 @@ set(IMPL_SOURCES
         ${HEADER_DIR}/internal/catch_debug_console.cpp
         ${HEADER_DIR}/internal/catch_debugger.cpp
         ${HEADER_DIR}/internal/catch_decomposer.cpp
+        ${HEADER_DIR}/internal/catch_enforce.cpp
         ${HEADER_DIR}/internal/catch_errno_guard.cpp
         ${HEADER_DIR}/internal/catch_exception_translator_registry.cpp
         ${HEADER_DIR}/internal/catch_fatal_condition.cpp