add var-ref->mod-decl-insp' and switch cur-code-insp' uses

Macros and other tools that need syntax privilege used
`(current-code-inspector)' at the module top-level to try to
capture the right code inspector at load time. It's more
consistent to instead use the enclosing module's declaration-time
inspector, and `var-ref->mod-decl-insp' provides that. The
new function works only on references to anonymous variables,
which limits access to the inspector.

The real function name is longer, of course.

original commit: 0197902309c5400d463393829a88282c627dafd2

collects/mzlib/private/package-helper.rkt

@@ -46,7 +46,8 @@
      ((bound-identifier=? id (caar renames)) (car renames))
      (else (stx-assoc id (cdr renames)))))
   
-  (define insp (current-code-inspector))
+  (define insp (variable-reference->module-declaration-inspector
+                (#%variable-reference)))
 
   (define (rebuild ctxt val)
     (if (syntax? ctxt)

collects/mzlib/shared.rkt

@@ -9,7 +9,8 @@
 
 (provide shared)
 
-(define-for-syntax code-insp (current-code-inspector))
+(define-for-syntax code-insp (variable-reference->module-declaration-inspector
+                              (#%variable-reference)))
 
 (define undefined (letrec ([x x]) x))
 (require (only-in scheme/base [cons the-cons]))

collects/racket/package.rkt

@@ -102,7 +102,8 @@
                  orig
                  orig))
 
-(define-for-syntax code-insp (current-code-inspector))
+(define-for-syntax code-insp (variable-reference->module-declaration-inspector
+                              (#%variable-reference)))
 (define-for-syntax (disarm* stx)
   (cond
    [(and (syntax? stx)