yanglint REFACTOR new yl_opt and cmd callbacks

The yanglint options were stored in non-interactive mode in the
structure named 'context'. This structure was renamed to yl_opt
and is now also used in the interactive mode, which has also been
expanded with new callbacks. These callbacks are the basis for
further refactoring commits, which aim to reduce duplicate code
between interactive and non-interactive modes to a minimum.
diff --git a/tools/lint/CMakeLists.txt b/tools/lint/CMakeLists.txt
index dd052d8..9ff39b2 100644
--- a/tools/lint/CMakeLists.txt
+++ b/tools/lint/CMakeLists.txt
@@ -18,6 +18,10 @@
     cmd_print.c
     cmd_searchpath.c
     cmd_extdata.c
+    cmd_help.c
+    cmd_verb.c
+    cmd_debug.c
+    yl_opt.c
     common.c
 )
 if(YANGLINT_INTERACTIVE)