tree schema UPDATE schema mount support for lys_getnext

... which also adds the support for lys_find_xpath_atoms().
diff --git a/src/xpath.c b/src/xpath.c
index 578324a..b83e1cc 100644
--- a/src/xpath.c
+++ b/src/xpath.c
@@ -6673,6 +6673,9 @@
     if (options & LYXP_SCNODE_OUTPUT) {
         getnext_opts |= LYS_GETNEXT_OUTPUT;
     }
+    if (options & LYXP_SCNODE_SCHEMAMOUNT) {
+        getnext_opts |= LYS_GETNEXT_WITHSCHEMAMOUNT;
+    }
 
     orig_used = set->used;
     for (i = 0; i < orig_used; ++i) {