Fix codegen of do-while condition

The condition of a do-while loop can use variables declared in the loop
(variables can only be declared inside a block). Previously this behaviour
caused crash because after the block was generated, all variables declared
inside that block were gone from myFrameMap

 #KT-3280 Fixed

compiler/testData/codegen/box/controlStructures/doWhileFib.kt

@@ -0,0 +1,12 @@
+fun box(): String {
+    var fx = 1
+    var fy = 1
+    
+    do {
+        var tmp = fy
+        fy = fx + fy
+        fx = tmp
+    } while (fy < 100)
+    
+    return if (fy == 144) "OK" else "Fail $fx $fy"
+}