Merge branch 'master' into make_fix

doc/jvm/index.md

@@ -13,6 +13,8 @@ Before you install XGBoost4J, you need to define environment variable `JAVA_HOME
 
 After your `JAVA_HOME` is defined correctly, it is as simple as run `mvn package` under jvm-packages directory to install XGBoost4J.
 
+NOTE: XGBoost4J requires to run with Spark 1.6 or newer 
+
 Contents
 --------
 * [Java Overview Tutorial](java_intro.md)

include/xgboost/c_api.h

@@ -266,7 +266,7 @@ XGB_DLL int XGDMatrixNumCol(DMatrixHandle handle,
  * \param out handle to the result booster
  * \return 0 when success, -1 when failure happens
  */
-XGB_DLL int XGBoosterCreate(void* dmats[],
+XGB_DLL int XGBoosterCreate(const DMatrixHandle dmats[],
                             bst_ulong len,
                             BoosterHandle *out);
 /*!

src/c_api/c_api.cc

@@ -463,7 +463,7 @@ int XGDMatrixNumCol(const DMatrixHandle handle,
 }
 
 // xgboost implementation
-int XGBoosterCreate(DMatrixHandle dmats[],
+int XGBoosterCreate(const DMatrixHandle dmats[],
                     bst_ulong len,
                     BoosterHandle *out) {
   API_BEGIN();