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

build.xml

@@ -516,8 +516,8 @@
         <cleandir dir="${output}/classes/runtime"/>
         <javac2 destdir="${output}/classes/runtime" debug="true" debuglevel="lines,vars,source" includeAntRuntime="false" source="${java.target}" target="${java.target}">
             <withKotlin/>
-            <src path="${basedir}/runtime/src"/>
-            <src path="${basedir}/runtime/kt"/>
+            <src path="${basedir}/core/builtins/src"/>
+            <src path="${basedir}/core/runtime.jvm/src"/>
         </javac2>
 
         <cleandir dir="${output}/classes/stdlib"/>
@@ -552,7 +552,9 @@
 
     <target name="runtime_sources">
         <jar destfile="${kotlin-home}/lib/kotlin-runtime-sources.jar">
-            <fileset dir="${basedir}/runtime/src" includes="**/*"/>
+            <fileset dir="${basedir}/core/builtins/native" includes="**/*"/>
+            <fileset dir="${basedir}/core/builtins/src" includes="**/*"/>
+            <fileset dir="${basedir}/core/runtime.jvm/src" includes="**/*"/>
             <fileset dir="${basedir}/libraries/stdlib/src" includes="**/*"/>
             <zipfileset file="${kotlin-home}/build.txt" prefix="META-INF"/>