Formal comments for line directives are parsed too strictly in 20210117

[nrnrnr]

At some point between 20130715 (Debian stable) and 20210117, MLton stopped accepting line directives like the following:

(*#line 407 "lazyparse.nw"*)

MLton now requires a column number, e.g.,

(*#line 407.1 "lazyparse.nw"*)

This change is unfriendly to legacy code, and also, the full syntax appears as if it may be incompatible with SML/NJ's syntax for #line directives.

Please update MLton so it can default the column to 1 and it can also accept the same syntax as SML/NJ. (We SMLers have to stick together!)