String <-> CharArray conversion, ArrayBuilder by @elizarov (#98)

backend.native/tests/build.gradle

@@ -314,6 +314,11 @@ task tostring1(type: RunKonanTest) {
     source = "runtime/basic/tostring1.kt"
 }
 
+task tostring2(type: RunKonanTest) {
+    goldValue = "H e l l o \nHello\n"
+    source = "runtime/basic/tostring2.kt"
+}
+
 task array0(type: RunKonanTest) {
     goldValue = "5\n6\n7\n8\n9\n10\n11\n12\n13\n"
     source = "runtime/basic/array0.kt"
@@ -444,6 +449,11 @@ task moderately_large_array(type: RunKonanTest) {
     source = "runtime/collections/moderately_large_array.kt"
 }
 
+task string_builder0(type: RunKonanTest) {
+    goldValue = "OK\n"
+    source = "runtime/text/string_builder0.kt"
+}
+
 task catch1(type: RunKonanTest) {
     goldValue = "Before\nCaught Throwable\nDone\n"
     source = "runtime/exceptions/catch1.kt"