Silence "X needs to have dll-interface to be used by clients of class Y" warnings.

git-svn-id: http://root.cern.ch/svn/root/trunk@41884 27541ba8-7e3a-0410-8455-c3a389f83636

build/win/w32pragma.h

@@ -49,6 +49,8 @@
 #pragma warning (disable: 4748)
 /* function(): resolved overload was found by argument-dependent lookup */
 #pragma warning (disable: 4675)
+/* X needs to have dll-interface to be used by clients of class Y */
+#pragma warning (disable: 4251)
 
 /* function is hidden */
 #pragma warning (3: 4266)