Fix compilation on visual studio.

Change the fix made in d6eb388 because it does not compile on visual
studio in release mode where floor is an intrinsic function (which you
apparently may not define yourself even when not including <math.h>.

Author: Marcel Meulemans

json-builder.c

@@ -38,10 +38,6 @@
     #define snprintf _snprintf
 #endif
 
-static double floor(double d) {
-       return d - ((int)d % 1);
-}
-
 static const json_serialize_opts default_opts =
 {
    json_serialize_mode_single_line,
@@ -668,8 +664,11 @@ size_t json_measure_ex (json_value * value, json_serialize_opts opts)
 
             total += snprintf (NULL, 0, "%g", value->u.dbl);
 
-            if (value->u.dbl - floor (value->u.dbl) < 0.001)
-                total += 2;
+            /* Because sometimes we need to add ".0" if sprintf does not do it
+             * for us. Downside is that we allocate more bytes than strictly
+             * needed for serialization.
+             */
+            total += 2;
 
             break;