Fix breakage on old versions of SuiteSparse.

Thanks to Fisher Yu for reporting this.

Change-Id: Iefa89816cbb60e3512338a7c2a65655c017877ac

internal/ceres/suitesparse.h

diff --git a/internal/ceres/suitesparse.h b/internal/ceres/suitesparse.h
index 859e20e..5797160 100644
--- a/internal/ceres/suitesparse.h
+++ b/internal/ceres/suitesparse.h
@@ -60,9 +60,11 @@
 #endif
 
 // UF_long is deprecated but SuiteSparse_long is only available in
-// newer versions of SuiteSparse.
-#if (SUITESPARSE_VERSION < 4002)
-typedef UF_long SuiteSparse_long;
+// newer versions of SuiteSparse. So for older versions of
+// SuiteSparse, we define SuiteSparse_long to be the same as UF_long,
+// which is what recent versions of SuiteSparse do anyways.
+#ifndef SuiteSparse_long
+#define SuiteSparse_long UF_long;
 #endif
 
 namespace ceres {