Use rand/srand instead of random/srandom on Windows

random/srandom are not C standard functions.
Use standard rand/srand on Windows.

XClib/beefleg.h

@@ -8,6 +8,10 @@
 
 #define nmax 30
 
+#ifdef _WIN32
+#define random rand
+#endif
+
 extern void dgemv_(const char *, const int *, const int *, const double *,
     double *, const int *, double *, const int *, const double *, double *,
     const int *);

XClib/beefun.c

@@ -9,6 +9,10 @@
 
 #include "pbecor.h"
 
+#ifdef _WIN32
+#define srandom srand
+#endif
+
 // evaluate bee exchange energy and its derivatives de/drho and ( de/d|grad rho| ) / |grad rho|
 #pragma acc routine seq
 void beefx_(double *r, double *g, double *e, double *dr, double *dg, int *addlda)