Fix way how function table is built. Allows to extend Exception class. (#210)

backend.native/tests/build.gradle

@@ -653,6 +653,11 @@ task catch7(type: RunKonanTest) {
     source = "runtime/exceptions/catch7.kt"
 }
 
+task extend_exception(type: RunKonanTest) {
+    goldValue = "OK\n"
+    source = "runtime/exceptions/extend0.kt"
+}
+
 task catch3(type: RunKonanTest) {
     goldValue = "Before\nCaught Throwable\nDone\n"
     source = "codegen/try/catch3.kt"

backend.native/tests/runtime/exceptions/extend0.kt

@@ -0,0 +1,9 @@
+class C : Exception("OK")
+
+fun main(args: Array<String>) {
+    try {
+        throw C()
+    } catch (e: Throwable) {
+        println(e.message!!)
+    }
+}