Minor style cleanup

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Small refactoring to extraxt lexing methods

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Added support for Double literals

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Fixed but in integer primitives

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Added assertion, which helps RPython to compile with virtualizables

Signed-off-by: Stefan Marr <git@stefan-marr.de>