Fix QA check on version range syntax to detect use of ()'s
The problem was that we do the QA check on using the new version range syntax after parsing. The new syntax allows ()'s but previously the code threw them away in the parser stage. We now retain them in the AST and deal with them appropriately. This now allows the QA check to be accurate and detect things like "build-depends: base (>= 4.2)".