Bump up source/target version

Index: default.properties
--- default.properties.orig
+++ default.properties
@@ -28,7 +28,7 @@ build.compress = false
 junit.failonerror = true
 
 #  Minimum version of Java required to build the Wrapper
-javac.target.version=1.4
+javac.target.version=1.6
 
 #  Location of java to build the pre-release
 javac.dir=E:\\j2sdk1.4.2_19
