xml FEATURE xml parser

just work in progress:
- element name parser (lyxml_get_element())
diff --git a/src/common.h b/src/common.h
index 7fecf36..4f0157b 100644
--- a/src/common.h
+++ b/src/common.h
@@ -116,6 +116,8 @@
 #define LY_VCODE_INCHAR      LYVE_SYNTAX, "Invalid character 0x%x."
 #define LY_VCODE_INSTREXP    LYVE_SYNTAX, "Invalid character sequence \"%.*s\", expected %s."
 #define LY_VCODE_EOF         LYVE_SYNTAX, "Unexpected end-of-file."
+#define LY_VCODE_NTERM       LYVE_SYNTAX, "%s not terminated."
+#define LY_VCODE_NSUPP       LYVE_SYNTAX, "%s not supported."
 #define LY_VCODE_INSTMT      LYVE_SYNTAX_YANG, "Invalid keyword \"%s\"."
 #define LY_VCODE_INCHILDSTMT LYVE_SYNTAX_YANG, "Invalid keyword \"%s\" as a child of \"%s\"."
 #define LY_VCODE_DUPSTMT     LYVE_SYNTAX_YANG, "Duplicate keyword \"%s\"."