Fix build for gcc 8.2.1

wscript

@@ -220,6 +220,8 @@ def configure(conf):
 
     conf.env['BUILD_WERROR'] = not RELEASE
     add_cflag(conf, '-Wall')
+    add_cflag(conf, '-Wimplicit-fallthrough=0')
+    add_cflag(conf, '--warn-no-restrict')
     # lash_wrap code is generated by swig and causes warnings
     if not conf.env['BUILD_PYLASH']:
        add_cflag(conf, '-Wextra')