Add incomplet long double math support to libmingwex.a

winsup/mingw/mingwex/math/fdiml.c

@@ -0,0 +1,7 @@
+#include <math.h>
+
+long double
+fdiml (long double x, long double y)
+{
+   return  (isgreater(x, y) ? (x - y) : 0.0L);
+}