Hide std::exception_ptr and friends if exceptions disabled

Some compilers, e.g. the Green Hills C++ compiler, react badly to the
appearance of std::exception_ptr, std::current_exception,
std::rethrow_exception and std::uncaught_exception(s). To allow usage of
Catch2 with these compilers when exceptions are disabled, hide the usage
of std::exception_ptr etc. when compiling with
CATCH_CONFIG_DISABLE_EXCEPTIONS.

include/internal/catch_registry_hub.cpp

@@ -59,7 +59,11 @@ namespace Catch {
                 m_tagAliasRegistry.add( alias, tag, lineInfo );
             }
             void registerStartupException() noexcept override {
+#if !defined(CATCH_CONFIG_DISABLE_EXCEPTIONS)
                 m_exceptionRegistry.add(std::current_exception());
+#else
+                CATCH_INTERNAL_ERROR("Attempted to register active exception under CATCH_CONFIG_DISABLE_EXCEPTIONS!");
+#endif
             }
             IMutableEnumValuesRegistry& getMutableEnumValuesRegistry() override {
                 return m_enumValuesRegistry;

include/internal/catch_startup_exception_registry.cpp

@@ -9,6 +9,7 @@
 #include "catch_startup_exception_registry.h"
 #include "catch_compiler_capabilities.h"
 
+#if !defined(CATCH_CONFIG_DISABLE_EXCEPTIONS)
 namespace Catch {
 void StartupExceptionRegistry::add( std::exception_ptr const& exception ) noexcept {
         CATCH_TRY {
@@ -24,3 +25,4 @@ void StartupExceptionRegistry::add( std::exception_ptr const& exception ) noexce
     }
 
 } // end namespace Catch
+#endif

include/internal/catch_startup_exception_registry.h

@@ -15,11 +15,13 @@
 namespace Catch {
 
     class StartupExceptionRegistry {
+#if !defined(CATCH_CONFIG_DISABLE_EXCEPTIONS)
     public:
         void add(std::exception_ptr const& exception) noexcept;
         std::vector<std::exception_ptr> const& getExceptions() const noexcept;
     private:
         std::vector<std::exception_ptr> m_exceptions;
+#endif
     };
 
 } // end namespace Catch

include/internal/catch_uncaught_exceptions.cpp

@@ -12,7 +12,9 @@
 
 namespace Catch {
     bool uncaught_exceptions() {
-#if defined(CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS)
+#if defined(CATCH_CONFIG_DISABLE_EXCEPTIONS)
+        return false;
+#elif defined(CATCH_CONFIG_CPP17_UNCAUGHT_EXCEPTIONS)
         return std::uncaught_exceptions() > 0;
 #else
         return std::uncaught_exception();