Smart casts for local variables not captured in a closure and not changed in a loop, see #KT-3175.

isLocalVariable added. Assignment / initialization analysis.
Control whether a variable is changed in a loop at the beginning and at the end of the loop.
Control whether a variable is captured in a closure. #KT-3175  Fixed. #KT-2266  Fixed.
Tests for variable null safety and for variables is/as operations.
Loop / closure / variable property tests are included.
Old tests changed in accordance with KT-3175. In particular, all three of testSmartcastImpossible were fixed.

compiler/testData/diagnostics/tests/smartCasts/varnotnull/varCapturedInInlineClosure.kt

@@ -0,0 +1,15 @@
+// See also KT-7186
+
+fun IntArray.forEachIndexed( op: (i: Int, value: Int) -> Unit) {
+    for (i in 0..this.size()-1)
+        op(i, this[i])
+}
+
+fun max(a: IntArray): Int? {
+    var maxI: Int? = null
+    a.forEachIndexed { i, value ->
+        if (maxI == null || value >= a[<!TYPE_MISMATCH!>maxI<!>])
+            maxI = i
+    }
+    return maxI
+}