Apprently new VS headers (or other Win .h) drop "#define NAN".

This PR defines it when it«s not found (Windows only)

src/gmt_common_math.h

@@ -65,6 +65,17 @@ extern "C" {
 #	define int64_abs(x) ((int64_t)(((x) >= 0) ? (x) : -(x)))
 #endif
 
+/* Apparently NAN may not be defined anymore in new Visual Studio headers.
+  See https://github.com/conda-forge/gmt-feedstock/pull/302#issuecomment-2487473474
+  I found it in, and recopying it here:
+  "C:\Program Files (x86)\Windows Kits\10\Include\10.0.22000.0\ucrt\corecrt_math.h"
+*/
+#ifdef _WIN32
+#	ifndef NAN
+#		define NAN  (-(float)(((float)(1e+300 * 1e+300)) * 0.0F))
+#	endif
+#endif
+
 #ifdef __CYGWIN__	/* See http://gmt.soest.hawaii.edu/boards/1/topics/5428 */
 #ifdef __x86_64
 #define lrint(x) ((long int)(int)lrint(x))