flex-2.5.31 compatibility

[David Relson]

Matthias,

To correct one of the release notes, the parser is _not_ presently 
flex-2.5.31 compatible.  I can make it compatible (by removing 
%never-interactive), but have not yet done so.

It's apparent that %never-interactive affects how parsing operates.  It's 
not apparent whether flex-2.5.4 has it right or whether flex-2.5.31 has it 
right.  Before making the change, I'd like to know the answer to which flex 
is right.

Possibly, based on flex version, when compiling the .l file we can use 
options -I or -B (as appropriate).

Dvaid