add comment to compiler_warnings.supp

support-files/compiler_warnings.supp:
  add comment to make this file more useful

support-files/compiler_warnings.supp

+#
+# This file contains compiler warnings that can
+# be ignored for various reasons.
+#
+
 integer.cpp: .*control reaches end of non-void function.*: 1288-1427
 DictTabInfo.cpp : .*invalid access to non-static.*
 DictTabInfo.cpp : .*macro was used incorrectly.*