Check that function declarations don't use a reserved name Reserved function names are now caught if the function is just declared without being called in the shader source. Actually, function calls don't need to be checked for reserved names, since that just generates a redundant error message if function declarations are being checked. Includes some cleanup of ParseContext::checkIsNotReserved. It doesn't need special handling of built-in symbols, as they are never passed to the function. BUG=chromium:739448 TEST=angle_unittests Change-Id: I7115e1a7509626b5109b5c054c0704b0c3c19c58 Reviewed-on: https://chromium-review.googlesource.com/561457 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>