Adding unsized arrays to the glsl parser

Unsized arrays declare with an empty [] without
a specified size are now supported properly in
the glsl parser.

Also moved the construction code from the parser
into TParseContext.

Change-Id: Ic7b3efeee51da1a264e26af4d7908e7d2fccebd9
Reviewed-on: https://swiftshader-review.googlesource.com/3520
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>