Don't clear out all messages upon printing an assertion.

Previously, this would not print out any messages for the last CHECK
```cpp
TEST_CASE("Foo") {
INFO("Test case start");
for (int i = 0; i < 2; ++i) {
INFO("The number is " << i);
CHECK(i == 0);
}
CHECK(false);
}
```

now it does.

include/internal/catch_run_context.hpp

@@ -145,8 +145,9 @@ namespace Catch {
                 m_totals.assertions.failed++;
             }
 
-            if( m_reporter->assertionEnded( AssertionStats( result, m_messages, m_totals ) ) )
-                m_messages.clear();
+            // We have no use for the return value (whether messages should be cleared), because messages were made scoped
+            // and should be let to clear themselves out.
+            static_cast<void>(m_reporter->assertionEnded(AssertionStats(result, m_messages, m_totals)));
 
             // Reset working state
             m_lastAssertionInfo = AssertionInfo( std::string(), m_lastAssertionInfo.lineInfo, "{Unknown expression after the reported line}" , m_lastAssertionInfo.resultDisposition );