array literal parse problems in TreeParser

[Stephen Siegel]

Array literals are sometimes parsed incorrectly. See test2 in example literal directory. Literal {{1,2},{3,4},{5,6}} is interpreted as {{5,6}_}.

Also, the front end forbids array declarations in which the extent is not specified, e.g. "int x[];" However there are cases where this should be allowed, as in "int x[]={1,2,3};". See test3 in literal. The front end should just not check for this and leave it to the model layer to throw a syntax exception in the right places.