language/units: do not quantize
compiler/tools: add eval_constant and Fraction support
compiler/fold_constants: use eval_constant from tools
compiler/inline: cleanup reference manager, recognize Fraction
compiler/interleave: use eval_constant from tools
compiler/ir: compile fractions with denominator==1 as integers
compiler/lower_time: adapt to new unit system
language/core: remove unneeded import
compiler: use value_to_ast(x) instead of ast.Num(x)