scripts: Reverted del to resolve shadowed builtins

I don't know how I completely missed that this doesn't actually work!

Using del _does_ work in Python's repl, but it makes sense the repl may
differ from actual function execution in this case.

The problem is Python still thinks the relevant builtin is a local
variables after deletion, raising an UnboundLocalError instead of
performing a global lookup. In theory this would work if the variable
could be made global, but since global/nonlocal statements are lifted,
Python complains with "SyntaxError: name 'list' is parameter and
global".

And that's A-Ok! Intentionally shadowing language builtins already puts
this code deep into ugly hacks territory.

scripts/dbgrbyd.py

@@ -948,7 +948,8 @@ class JumpArt:
 
     @classmethod
     def fromrbyd(cls, rbyd, all=False):
-        all_ = all; del all
+        import builtins
+        all_, all = all, builtins.all
 
         jumps = []
         j_ = 4
@@ -1100,7 +1101,8 @@ class LifetimeArt:
 
     @classmethod
     def fromrbyd(cls, rbyd, all=False):
-        all_ = all; del all
+        import builtins
+        all_, all = all, builtins.all
 
         # first figure out where each rid comes from
         id = 0