make ASTs shared again

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/PythonLanguage.java

@@ -76,7 +76,7 @@
 import com.oracle.truffle.api.source.Source;
 import com.oracle.truffle.api.source.Source.SourceBuilder;
 
-@TruffleLanguage.Registration(id = PythonLanguage.ID, name = PythonLanguage.NAME, version = PythonLanguage.VERSION, mimeType = PythonLanguage.MIME_TYPE, interactive = true, internal = false, contextPolicy = TruffleLanguage.ContextPolicy.EXCLUSIVE)
+@TruffleLanguage.Registration(id = PythonLanguage.ID, name = PythonLanguage.NAME, version = PythonLanguage.VERSION, mimeType = PythonLanguage.MIME_TYPE, interactive = true, internal = false, contextPolicy = TruffleLanguage.ContextPolicy.SHARED)
 @ProvidedTags({StandardTags.CallTag.class, StandardTags.StatementTag.class, StandardTags.RootTag.class, StandardTags.TryBlockTag.class, DebuggerTags.AlwaysHalt.class})
 public final class PythonLanguage extends TruffleLanguage<PythonContext> {
     public static final String ID = "python";