More portability fixing for bipartite_match.c.

<float.h> is required for isinf() on some platforms.  Per buildfarm.

src/backend/lib/bipartite_match.c

@@ -16,6 +16,7 @@
  */
 #include "postgres.h"
 
+#include <float.h>
 #include <math.h>
 #include <limits.h>