Update Android.mk

Add callbacks.cc and summary_utils.cc.

Change-Id: Ia356b0c82138ca4c2235015986deff0e30b37304

jni/Android.mk

diff --git a/jni/Android.mk b/jni/Android.mk
index 23e588f..573994b 100644
--- a/jni/Android.mk
+++ b/jni/Android.mk
@@ -113,6 +113,7 @@
                    $(CERES_SRC_PATH)/block_random_access_sparse_matrix.cc \
                    $(CERES_SRC_PATH)/block_sparse_matrix.cc \
                    $(CERES_SRC_PATH)/block_structure.cc \
+                   $(CERES_SRC_PATH)/callbacks.cc \
                    $(CERES_SRC_PATH)/canonical_views_clustering.cc \
                    $(CERES_SRC_PATH)/cgnr_solver.cc \
                    $(CERES_SRC_PATH)/compressed_row_jacobian_writer.cc \
@@ -165,6 +166,7 @@
                    $(CERES_SRC_PATH)/sparse_normal_cholesky_solver.cc \
                    $(CERES_SRC_PATH)/split.cc \
                    $(CERES_SRC_PATH)/stringprintf.cc \
+                   $(CERES_SRC_PATH)/summary_utils.cc \
                    $(CERES_SRC_PATH)/suitesparse.cc \
                    $(CERES_SRC_PATH)/triplet_sparse_matrix.cc \
                    $(CERES_SRC_PATH)/trust_region_minimizer.cc \