[grammar] rdf:type shorthand a isn't properly recognized inside bnode literal

[Peter Geil]

When written inside a bnode literal on a separate line (optionally preceded by whitespace chars) the language grammar won't match it.

Example:

ex:Subj ex:pred [ a ex:ClassA;   # matched
    a ex:ClassB;                 # not matched
a ex:ClassC;                     # not matched
].

[Peter Geil]

Fixed + closed with: e709c72