quick diff performance: use equivalence class to compute quick diff

Modified (>) and added(+) files:

+org.eclipse.ui.internal.texteditor.quickdiff.compare.equivalence
+    DJBHashFunction.java
+    DocEquivalenceComparator.java
+    DocumentEquivalenceClass.java
+    Hash.java
+    IHashFunction.java
+    IntHash.java
+    SystemHashFunction.java

>org.eclipse.ui.internal.texteditor.quickdiff.compare.rangedifferencer
>    RangeDifference.java

>org.eclipse.ui.internal.texteditor.quickdiff
>    DocumentLineDiffer.java

>org.eclipse.jdt.text.tests.performance
>    PerformanceTestSuite.java
+    AbstractDocumentLineDifferTest.java
+    DocumentLineDifferInitializationText.java
+    DocumentLineDifferModificationTest.java
+    faust1.txt
9 files changed