[strong] Implement per-object restrictions behaviour of delete operator

src/messages.h

Index: src/messages.h
diff --git a/src/messages.h b/src/messages.h
index 75314e93f989fcd9d041f9679d4607d2b625bd11..c2c2e8dad6bf61ce1a284d6f416915f42e8efa39 100644
--- a/src/messages.h
+++ b/src/messages.h
@@ -226,6 +226,9 @@ class CallSite {
   T(StrictReadOnlyProperty, "Cannot assign to read only property '%' of %")    \
   T(StrongArity,                                                               \
     "In strong mode, calling a function with too few arguments is deprecated") \
+  T(StrongDeleteProperty,                                                      \

[rossberg, 2015/05/22 11:34:50]

Perhaps we should stylise strong object error messages consistently. E.g. always
always formulating them akin to

"On strong object %, property % cannot be deleted"

or something.

[conradw, 2015/05/22 13:37:56]

Done.

+    "Cannot delete property '%'; property deletion from strong object % is "   \
+    "deprecated")                                                              \
   T(StrongImplicitCast, "In strong mode, implicit conversions are deprecated") \
   T(SymbolKeyFor, "% is not a symbol")                                         \
   T(SymbolToPrimitive,                                                         \