No yy::parser::syntax_error if GLR

[Askar Safin]

Hi. I attempted to throw yy::parser::syntax_error from flex input file 
scanner.lpp and failed. I used GLR bison parser. Here is test code: 
https://paste.gg/p/anonymous/1d2fc78e88f444b0b8203bb3c20f8a53 . It seems 
yy::parser::syntax_error doesn't work GLR. It seems there is no definition for 
constructor and there is no code in parser for catching such exception.

So, please, fix. Or at least write in docs, that this is not supported. Of 
course, manual should document all features not supported in GLR.

And please give some workaround. What should I call in scanner file in case of 
error if I want GLR parser to exit gracefully and return non-zero from p.parse 
()? The only way I see is to define some special token, say, _ERROR, and return 
it from scanner in case of error.

==
Askar Safin
http://vk.com/safinaskar