Store only data for variables declared in current lexical scope.

Remove data for other variables (when leaving a scope).

compiler/testData/cfg-variables/lexicalScopes/whileScope.instructions

@@ -15,11 +15,11 @@ L0:
     mark(while (true) { val a: Int })
 L2 [loop entry point]:
 L5 [condition entry point]:
-    r(true)                                                   INIT: in: {a=D} out: {a=D}
+    r(true)
 L4 [body entry point]:
   3 mark({ val a: Int })
-    v(val a: Int)
-  2 jmp(L2 [loop entry point])                                                              USE: in: {} out: {}
+    v(val a: Int)                                             INIT: in: {} out: {a=D}
+  2 jmp(L2 [loop entry point])                                INIT: in: {} out: {}       USE: in: {} out: {}
 L3 [loop exit point]:
 -   read (Unit)
 -   mark("after")
@@ -29,5 +29,5 @@ L1:
 error:
     <ERROR>
 sink:
-    <SINK>                                                                                  USE: in: {} out: {}
+    <SINK>                                                                               USE: in: {} out: {}
 =====================