Add more explicit system includes (fix build on master)

knizhnik · knizhnik · commit df44e1ad4b12 · 2017-03-14T16:07:15.000+03:00
diff --git a/vops.c b/vops.c
@@ -1,5 +1,7 @@
 #include "postgres.h"
 
+#include <float.h>
+#include <math.h>
 #include "funcapi.h"
 #include "miscadmin.h"
 
