data parsers CHANGE print/parse anyxml in JSON format

Store anyxml in JSON as XML string. Some anyxml support is necessary
for NETCONF filters and rpcs in general since anyxml is used there
quite intensively.
diff --git a/src/xml.c b/src/xml.c
index ae4648f..91e7299 100644
--- a/src/xml.c
+++ b/src/xml.c
@@ -890,8 +890,8 @@
 }
 
 /* logs directly */
-static struct lyxml_elem *
-parse_elem(struct ly_ctx *ctx, const char *data, unsigned int *len, struct lyxml_elem *parent)
+struct lyxml_elem *
+lyxml_parse_elem(struct ly_ctx *ctx, const char *data, unsigned int *len, struct lyxml_elem *parent)
 {
     const char *c = data, *start, *e;
     const char *lws;    /* leading white space for handling mixed content */
@@ -1088,7 +1088,7 @@
                     lyxml_add_child(ctx, elem, child);
                     elem->flags |= LYXML_ELEM_MIXED;
                 }
-                child = parse_elem(ctx, c, &size, elem);
+                child = lyxml_parse_elem(ctx, c, &size, elem);
                 if (!child) {
                     goto error;
                 }
@@ -1222,7 +1222,7 @@
         }
     }
 
-    root = parse_elem(ctx, c, &len, NULL);
+    root = lyxml_parse_elem(ctx, c, &len, NULL);
     if (!root) {
         if (first) {
             LY_TREE_FOR_SAFE(first, next, root) {