reduce warnings when compiling unit tests

svn path=/trunk/mcs/; revision=43116

mcs/class/System.Drawing/Makefile

@@ -6,6 +6,6 @@ LIBRARY = System.Drawing.dll
 
 LIB_MCS_FLAGS = /unsafe /r:$(corlib) /r:System.dll /nowarn:649 /nowarn:169
 
-TEST_MCS_FLAGS = $(LIB_MCS_FLAGS) /nowarn:618 /r:System.Drawing.dll 
+TEST_MCS_FLAGS = $(LIB_MCS_FLAGS) /r:System.Drawing.dll -nowarn:0618 -nowarn:219 -nowarn:169
 
 include ../../build/library.make