Merge branch 'gcc9.AthenaMP-20190320' into 'master'

AthenaMP: Fix gcc9 warnings.

See merge request atlas/athena!22060

Control/AthenaMP/src/memory-monitor/rapidjson/document.h

@@ -325,6 +325,8 @@ struct GenericStringRef {
     GenericStringRef(const CharType* str, SizeType len)
         : s(str), length(len) { RAPIDJSON_ASSERT(s != NULL); }
 
+    GenericStringRef( const GenericStringRef& ) = default;
+
     //! implicit conversion to plain CharType pointer
     operator const Ch *() const { return s; }