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/kt3280.kt

@@ -0,0 +1,24 @@
+fun foo() {
+    var x = 0
+    do {
+        x++
+        var y = x + 5
+    } while (y < 10)
+    if (x != 5) throw AssertionError("$x")
+}
+
+fun bar() {
+    var b = false
+    do {
+        var x = "X"
+        var y = "Y"
+        b = true
+    } while (x + y != "XY")
+    if (!b) throw AssertionError()
+}
+
+fun box(): String {
+    foo()
+    bar()
+    return "OK"
+}