#5 Allow zero-length regular expressions in syntax definition

[VVV]

Thank you for great product.

Sometimes I need to use regular expressions in syntax files, for example when I want to start block but not parse first match as marker, i.e. if I want to start block on line in form [...]:

(?=\[.*\])

Such regular expression will return match with zero length, but it is still valid.

I updated 2 files to allow use of such regular expressions, they are attached. My comments are marked with //VVV.

Sincerely yours,
Viatcheslav V. Vassiliev

[VVV]

Updated files to allow zero-length regular expressions.