Resolve undefined M_PI w/ MSVC2013

diff --git a/extern/curve_fit_nd/intern/curve_fit_cubic_refit.c b/extern/curve_fit_nd/intern/curve_fit_cubic_refit.c
index 46445467869390790dfa7f6a4d76078897640e0b..c78b79d76ef457d588ce3025d0faf89ec800170a 100644 (file)
--- a/extern/curve_fit_nd/intern/curve_fit_cubic_refit.c
+++ b/extern/curve_fit_nd/intern/curve_fit_cubic_refit.c
@@ -43,6 +43,10 @@
  *   While re-fitting, remove knots that fall below the error threshold.
  */
 
+#ifdef _MSC_VER
+#  define _USE_MATH_DEFINES
+#endif
+
 #include <math.h>
 #include <float.h>
 #include <stdbool.h>