[dmap] Change date type to int64, fix for "Integer value too large"

uint32 won't work for dates before the Unix epoch, and int32 won't work after
2038, so let's see if clients can handle int64.

Resolves #1742

src/dmap_common.c

@@ -224,7 +224,6 @@ dmap_add_field(struct evbuffer *evbuf, const struct dmap_field *df, char *strval
     {
       switch (df->type)
 	{
-	  case DMAP_TYPE_DATE:
 	  case DMAP_TYPE_UBYTE:
 	  case DMAP_TYPE_USHORT:
 	  case DMAP_TYPE_UINT:
@@ -247,6 +246,7 @@ dmap_add_field(struct evbuffer *evbuf, const struct dmap_field *df, char *strval
 	      val.v_u64 = 0;
 	    break;
 
+	  case DMAP_TYPE_DATE:
 	  case DMAP_TYPE_LONG:
 	    ret = safe_atoi64(strval, &val.v_i64);
 	    if (ret < 0)