upping the major version. lots of small (incompatible) changes, and the addition of int64 support.
diff --git a/tinyxml2.h b/tinyxml2.h
index 410faa2..9dcc345 100755
--- a/tinyxml2.h
+++ b/tinyxml2.h
@@ -96,7 +96,7 @@
 /* Versioning, past 1.0.14:

 	http://semver.org/

 */

-static const int TIXML2_MAJOR_VERSION = 3;

+static const int TIXML2_MAJOR_VERSION = 4;

 static const int TIXML2_MINOR_VERSION = 0;

 static const int TIXML2_PATCH_VERSION = 0;