Stacktrace manager optimization

Store `StacktTraceManager` directly in `GlobalEnv` to prevent a synchronized hashmap lookup on every `eval()` and `seval()` call.
Move `StackTraceManager` getter in `CClosure` to post-environment-clone to ensure that it does not overwrite the `StackTraceManager` of the original thread when called from a new thread(by for example `x_new_thread()`).

src/main/java/com/laytonsmith/core/constructs/CClosure.java

@@ -207,13 +207,18 @@ protected void execute(Mixed... values) throws ConfigRuntimeException, ProgramFl
 		if(node == null) {
 			return;
 		}
-		StackTraceManager stManager = env.getEnv(GlobalEnv.class).GetStackTraceManager();
-		stManager.addStackTraceElement(new ConfigRuntimeException.StackTraceElement("<<closure>>", getTarget()));
+		Environment environment;
 		try {
-			Environment environment;
 			synchronized(this) {
 				environment = env.clone();
 			}
+		} catch (CloneNotSupportedException ex) {
+			Logger.getLogger(CClosure.class.getName()).log(Level.SEVERE, null, ex);
+			return;
+		}
+		StackTraceManager stManager = environment.getEnv(GlobalEnv.class).GetStackTraceManager();
+		stManager.addStackTraceElement(new ConfigRuntimeException.StackTraceElement("<<closure>>", getTarget()));
+		try {
 			CArray arguments = new CArray(node.getData().getTarget());
 			CArray vararg = null;
 			CClassType varargType = null;

src/main/java/com/laytonsmith/core/environments/GlobalEnv.java

@@ -27,7 +27,6 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.WeakHashMap;
 import java.util.concurrent.ConcurrentHashMap;
 
 /**
@@ -54,7 +53,8 @@ public class GlobalEnv implements Environment.EnvironmentImpl, Cloneable {
 	private BoundEvent.ActiveEvent event = null;
 	private boolean interrupt = false;
 	private final List<Iterator> arrayAccessList = Collections.synchronizedList(new ArrayList<>());
-	private final WeakHashMap<Thread, StackTraceManager> stackTraceManagers = new WeakHashMap<>();
+	private Thread stackTraceManagerThread = null;
+	private StackTraceManager stackTraceManager = null;
 	private final MutableObject<Map<String, Mixed>> runtimeSettings
 			= new MutableObject<>(new ConcurrentHashMap<>());
 	private FileOptions fileOptions;
@@ -155,6 +155,8 @@ public EnvironmentImpl clone() throws CloneNotSupportedException {
 		} else if(!cloneVars) {
 			clone.iVariableList = new IVariableList(clone.iVariableList);
 		}
+		clone.stackTraceManager = this.stackTraceManager;
+		clone.stackTraceManagerThread = this.stackTraceManagerThread;
 		return clone;
 	}
 
@@ -344,14 +346,11 @@ public List<Iterator> GetArrayAccessIteratorsFor(ArrayAccess array) {
 	 */
 	public StackTraceManager GetStackTraceManager() {
 		Thread currentThread = Thread.currentThread();
-		synchronized(stackTraceManagers) {
-			StackTraceManager manager = stackTraceManagers.get(currentThread);
-			if(manager == null) {
-				manager = new StackTraceManager();
-				stackTraceManagers.put(currentThread, manager);
-			}
-			return manager;
+		if(this.stackTraceManager == null || currentThread != this.stackTraceManagerThread) {
+			this.stackTraceManager = new StackTraceManager();
+			this.stackTraceManagerThread = currentThread;
 		}
+		return this.stackTraceManager;
 	}
 
 	/**