Adopt Mandelbrot with proper literals

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Use primitive booleans to represent true and false

- added boolean support to type system and expression
- use native boolean for field and variable accesses
- introduced special replacements for globals access to *true, false, nil*

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