重构cache目录，将libxml2、libcurl放到vendor目录。

cache/src/tango_cache_xml.h

@@ -0,0 +1,12 @@
+#ifndef __TANGO_CACHE_XML_H__
+#define __TANGO_CACHE_XML_H__
+
+#include "tango_cache_client_in.h"
+
+bool parse_uploadID_xml(const char *content, int len, char **uploadID);
+void construct_complete_xml(struct tango_cache_ctx *ctx, char **xml, int *len);
+void construct_multiple_delete_xml(const char *bucket, char *key[], u_int32_t num, int is_hash, char **xml, size_t *len);
+bool parse_multidelete_xml(const char *xml, int len, u_int32_t *errnum, char *errstr, int size);
+
+#endif
+