Skip transitional keyword

This allows to parse configs with the transitional key
word. For a working version of the transitional feature it is
necessary to extend parsing of the default keyword to support
setting the value to a variable:
```
config NEW_BOOL
	bool "New bool option"
	default OLD_BOOL
```

Signed-off-by: Quirin Gylstorff <[email protected]>

Author: gylstorffq

kconfiglib.py

@@ -3151,6 +3151,8 @@ def _parse_props(self, node):
                 node.dep = self._make_and(node.dep,
                                           self._expect_expr_and_eol())
 
+            elif t0 is _T_TRANSITIONAL:
+                continue
             elif t0 is _T_HELP:
                 self._parse_help(node)
 
@@ -7010,9 +7012,10 @@ def _shell_fn(kconf, _, command):
     _T_SOURCE,
     _T_STRING,
     _T_TRISTATE,
+    _T_TRANSITIONAL,
     _T_UNEQUAL,
     _T_VISIBLE,
-) = range(1, 51)
+) = range(1, 52)
 
 # Keyword to token map, with the get() method assigned directly as a small
 # optimization
@@ -7059,6 +7062,7 @@ def _shell_fn(kconf, _, command):
     "source":         _T_SOURCE,
     "string":         _T_STRING,
     "tristate":       _T_TRISTATE,
+    "transitional":   _T_TRANSITIONAL,
     "visible":        _T_VISIBLE,
 }.get