gnulib-tool.py: Use function arguments instead of magic numbers. * pygnulib/GLEmiter.py (GLEmiter.autoconfSnippets): Remove the 'verifier' integer flag argument. Add the 'module_filter' function argument. Use it to determine if Autoconf snippets should be printed for each module. * pygnulib/GLImport.py (GLImport.gnulib_comp): Update call to use a lambda function. * pygnulib/GLTestDir.py (GLTestDir.execute): Likewise.