Improved assembler, support '+' operator

Now assemble :
- lem_splash.dasm
- hwtest.dasm
- clock.dasm
- lem1803.dasm
- test2.dasm
the syntax of tester.dasm is not correct and will be refused.
gnarfel.dasm/stillalive.dasm have errors... Negatives numbers are not
supported use hexa instead.
Know bugs : ';' in first character of line = error