Explicit ctor used to fix compilation failures caused by copy

initialization.

include/reporters/catch_reporter_multi.cpp

@@ -19,7 +19,7 @@ namespace Catch {
     }
 
     std::set<Verbosity> MultipleReporters::getSupportedVerbosities() {
-        return { };
+        return std::set<Verbosity>{ };
     }