Walls accepts undocumented LRUD at station syntax

[jedwards1211]

The Walls Manual has examples of specifying an LRUD at a station:

A	*3 4 5 6*

However, it also allows - to be used in the from or to station field, which is undocumented:

-	C	*3 4 5 6*
D	-	*3 4 5 6*

I can confirm it interpreted these as LRUD at station lines because it produced the non-fatal error message "LRUD at station - ignored. Facing direction can't be determined."