Reduce memory consumption of the typical LocationImpl
I recently noticed very heavy memory usage on our testsuite (which is using mockito) so I started profiling.

I eventually found #1313 but that's already being worked on. Also spotted a low hanging fruit: our testsuite is allocating about 6 *million* instances of `LocationImpl`.
It looks like I can't avoid that easily, however each `LocationImpl` also allocates a new `StackTraceFilter`, which can be easily avoided when the default is being applied; sending a PR shortly.

This should save us about 6 million empty and pointless `StackTraceFilter` :)
src/main/java/org/mockito/internal/debugging/LocationImpl.java
src/main/java/org/mockito/internal/debugging/LocationImpl.java
diff --git a/src/main/java/org/mockito/internal/debugging/LocationImpl.java b/src/main/java/org/mockito/internal/debugging/LocationImpl.java
index ce3de04a0a..8561b62d3e 100644
--- a/src/main/java/org/mockito/internal/debugging/LocationImpl.java
+++ b/src/main/java/org/mockito/internal/debugging/LocationImpl.java
@@ -11,11 +11,14 @@
 public class LocationImpl implements Location, Serializable {
 
     private static final long serialVersionUID = -9054861157390980624L;
+    //Limit the amount of objects being created, as this class is heavily instantiated:
+    private static final StackTraceFilter defaultStackTraceFilter = new StackTraceFilter();
+
     private final Throwable stackTraceHolder;
     private final StackTraceFilter stackTraceFilter;
 
     public LocationImpl() {
-        this(new StackTraceFilter());
+        this(defaultStackTraceFilter);
     }
 
     public LocationImpl(StackTraceFilter stackTraceFilter) {
@@ -23,7 +26,7 @@ public LocationImpl(StackTraceFilter stackTraceFilter) {
     }
 
     public LocationImpl(Throwable stackTraceHolder) {
-        this(new StackTraceFilter(), stackTraceHolder);
+        this(defaultStackTraceFilter, stackTraceHolder);
     }
 
     private LocationImpl(StackTraceFilter stackTraceFilter, Throwable stackTraceHolder) {
