Move everything under kotlin-native folder

I was forced to manually do update the following files, because otherwise
they would be ignored according .gitignore settings. Probably they
should be deleted from repo.

Interop/.idea/compiler.xml
Interop/.idea/gradle.xml
Interop/.idea/libraries/Gradle__org_jetbrains_kotlin_kotlin_runtime_1_0_3.xml
Interop/.idea/libraries/Gradle__org_jetbrains_kotlin_kotlin_stdlib_1_0_3.xml
Interop/.idea/modules.xml
Interop/.idea/modules/Indexer/Indexer.iml
Interop/.idea/modules/Runtime/Runtime.iml
Interop/.idea/modules/StubGenerator/StubGenerator.iml
backend.native/backend.native.iml
backend.native/bc.frontend/bc.frontend.iml
backend.native/cli.bc/cli.bc.iml
backend.native/cli.bc/src/org/jetbrains/kotlin/cli/bc/K2Native.kt
backend.native/cli.bc/src/org/jetbrains/kotlin/cli/bc/K2NativeCompilerArguments.kt
backend.native/tests/link/lib/foo.kt
backend.native/tests/link/lib/foo2.kt
backend.native/tests/teamcity-test.property

kotlin-native/gradle/kotlinGradlePlugin.gradle

@@ -0,0 +1,37 @@
+def properties = ['buildKotlinVersion', 'buildKotlinCompilerRepo', 'kotlinVersion', 'kotlinCompilerRepo']
+
+for (prop in properties) {
+    if (!hasProperty(prop)) {
+        throw new GradleException("Please ensure the '$prop' property is defined before applying this script.")
+    }
+}
+
+project.buildscript.repositories {
+    maven {
+        url buildKotlinCompilerRepo
+    }
+    maven {
+        url kotlinCompilerRepo
+    }
+    maven {
+        url 'https://cache-redirector.jetbrains.com/maven-central'
+    }
+    mavenCentral()
+}
+
+project.buildscript.dependencies {
+    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
+}
+configurations {
+    kotlinCompilerClasspath
+}
+project.repositories {
+    maven { url buildKotlinCompilerRepo }
+    maven {
+        url kotlinCompilerRepo
+    }
+}
+
+project.dependencies {
+    kotlinCompilerClasspath("org.jetbrains.kotlin:kotlin-compiler-embeddable:$buildKotlinVersion")
+}