Remove the only test in the syntax module.  It ends up that the
transformer must handle this error case.

In the transformer, check for a list compression in com_assign_list()
by looking for a list_for node where a comma is expected.

In pycodegen.compile() re-raise the SyntaxError rather than catching
it and exiting

Invoke compiler.syntax.check() after building AST.  If a SyntaxError
occurs, print the error and exit without generating a .pyc file.

Refactor code to use compiler.misc.set_filename() rather than passing
filename argument around to each CodeGenerator instance.