Add WeakRef Implementation

TODO

@@ -47,7 +47,6 @@ Optimization ideas:
 - add implicit numeric strings for Uint32 numbers?
 - optimize `s += a + b`, `s += a.b` and similar simple expressions
 - ensure string canonical representation and optimise comparisons and hashes?
-- remove JSObject.first_weak_ref, use bit+context based hashed array for weak references
 - property access optimization on the global object, functions,
   prototypes and special non extensible objects.
 - create object literals with the correct length by backpatching length argument

doc/quickjs.texi

@@ -281,9 +281,7 @@ The following features are not supported yet:
 
 @item Tail calls@footnote{We believe the current specification of tails calls is too complicated and presents limited practical interests.}
 
-@item WeakRef and FinalizationRegistry objects
-
-@item Symbols as WeakMap keys
+@item FinalizationRegistry objects
 
 @end itemize
 

qjsc.c

@@ -77,6 +77,7 @@ static const FeatureEntry feature_list[] = {
 #define FE_MODULE_LOADER 9
     { "module-loader", NULL },
     { "bigint", "BigInt" },
+    { "weakref", "WeakRef" },
 };
 
 void namelist_add(namelist_t *lp, const char *name, const char *short_name,

quickjs-atom.h

@@ -269,5 +269,6 @@ DEF(Symbol_asyncIterator, "Symbol.asyncIterator")
 #ifdef CONFIG_BIGNUM
 DEF(Symbol_operatorSet, "Symbol.operatorSet")
 #endif
+DEF(WeakRef, "WeakRef")
 
 #endif /* DEF */