output builtin and configured entity refs in shrinked text

This fixes everything in issue #5 which is not about parsing internal
entities from the DTD, see #4.

testsuite/Test/StandOff/ShrinkedText.hs

@@ -112,6 +112,16 @@ test_charrefMappedChars = do
   validateMappedCharacters "charref"
 
 
+test_entityrefShrinkedTXT = do
+  validateShrinkedTXT "entityref"
+
+test_entityrefOffsetMapping = do
+  validateOffsetMapping "entityref"
+
+test_entityrefMappedEntitys = do
+  validateMappedCharacters "entityref"
+
+
 test_advancedShrinkedTXT = do
   validateShrinkedTXT "advanced"
 

testsuite/annotations-shrinked/entityref.shrinked.txt

@@ -0,0 +1,3 @@
+Lorem ipsum dolor sit am&, cons&&ur
+sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut
+labore & dolore magna aliquyam erat, sed diam voluptua.