MXMLTagAttributeData: fix location of MXML attribute value start column

It was incorrectly getting set to the start column of the = token instead of the end column
diff --git a/compiler/src/main/java/org/apache/royale/compiler/internal/mxml/MXMLTagAttributeData.java b/compiler/src/main/java/org/apache/royale/compiler/internal/mxml/MXMLTagAttributeData.java
index e88b9e0..8979bd8 100644
--- a/compiler/src/main/java/org/apache/royale/compiler/internal/mxml/MXMLTagAttributeData.java
+++ b/compiler/src/main/java/org/apache/royale/compiler/internal/mxml/MXMLTagAttributeData.java
@@ -87,7 +87,7 @@
 
             valueStart = token.getEnd(); // set the value's start to right after the equals until we have a value
             valueLine = token.getLine();
-            valueColumn = token.getColumn();
+            valueColumn = token.getColumn() + token.getEnd() - token.getStart();
         }
 
         Boolean firstToken = true;