mute cpplint runtime/casting messages for now

CPPLINT.cfg

@@ -1,7 +1,7 @@
 linelength=1000
 
 # lax
-filter=-build/include_subdir,-readability/casting,-build/include,-runtime/printf,-runtime/int,-runtime/arrays,-readability/fn_size,-runtime/threadsafe_fn,-readability/braces,-whitespace/braces,-build/header_guard,-whitespace/semicolon,-legal/copyright,-runtime/references
+filter=-build/include_subdir,-readability/casting,-build/include,-runtime/printf,-runtime/int,-runtime/arrays,-readability/fn_size,-runtime/threadsafe_fn,-readability/braces,-whitespace/braces,-build/header_guard,-whitespace/semicolon,-legal/copyright,-runtime/references,-runtime/casting
 
 # strict
 # filter=-build/include_subdir,-readability/casting,-build/include
@@ -49,6 +49,11 @@ filter=-build/include_subdir,-readability/casting,-build/include,-runtime/printf
 # [runtime/references]
 #     example: Is this a non-const reference? If so, make const or
 #              use a pointer: debug & HOT_DB_MAP
+#
+# [runtime/casting]
+#     example: Are you taking an address of a cast?  This is dangerous: could
+#              be a temp var.  Take the address before doing the cast, rather
+#              than after  
 
 # messages we can leave off
 # -------------------------