patch for PortletExporter.java:exportAssetTags(PortletDataContext) to improve page publishing performance

gistfile1.txt

		for (AssetTag assetTag : assetTags) {
			// CUSTOM START
			// By only exporting tags that are more recent than the export start
			// date of the Layout, we assume that at some point in time the
			// exporting Site and the importing Site had exactly the same Tags,
			// and that every Layout export will harvest any tags not found in
			// the importing Site
			if(portletDataContext.hasDateRange()) {
				int diff = DateUtil.compareTo(portletDataContext.getStartDate(),
					assetTag.getModifiedDate());
				if(diff == 0 || diff < 0) {
					exportAssetTag(portletDataContext, assetTag, rootElement);
				}
			} else {
				exportAssetTag(portletDataContext, assetTag, rootElement);
			}
			// CUSTOM END
		}