File Release Notes and Changelog

* fix: else blocks didn't get dropped correctly
* fix: parsing stopped after an #include
* syntax modifications (more caml-like):
 - allow indentation
 - "#define x value" -> "#let x = value"
 - "#default x value" -> "#let_default x = value"
* new #warning directive
* adding of the "<:optcomp< expr >>" quotation
* generation of dependencies for compilation with a makefile