Create module 'builtins', move 'runtime' -> 'runtime.jvm'

'builtins' will be used for platform-independent core built-in definitions,
'runtime.jvm' for things that should be present at runtime in order for Kotlin
code to execute correctly on JVM

ProgressionUtil goes to 'builtins' right now because progression iterators
depend on it, but should be rewritten to Kotlin later

libraries/tools/runtime/pom.xml

@@ -32,8 +32,8 @@
                             <target>
                                 <delete dir="${basedir}/target/copied-sources" failonerror="false" />
                                 <copy todir="${basedir}/target/copied-sources">
-                                    <fileset dir="${basedir}/../../../runtime/src"/>
-                                    <fileset dir="${basedir}/../../../runtime/kt"/>
+                                    <fileset dir="${basedir}/../../../core/builtins/src"/>
+                                    <fileset dir="${basedir}/../../../core/runtime.jvm/src"/>
                                 </copy>
                             </target>
                         </configuration>