[4/5] dtc: Cleanup yylloc type and handling

[Jon Loeliger]

> This patch makes several cleanups to the handling of location
> variables as they're carried through the parser.  Specifically:
> 
> 	- (for now) remove column numbers from YYLTYPE, since we were
> never correctly filling them in from the lexer in any case.

I fully implemented both line and column handling, as far as
I can tell, correctly.  Bug fixes welcome as needed, of course.

jdl