unfold, unfold-right, map etc.

	modified:   broom/core.brm
	modified:   tests/core_test.brm
"not" builtin.
"true/false" as literal, not symbol
	modified:   broom/builtin.go
	modified:   broom/read.go
Evals arg of method invoke.
	modified:   broom/builtin.go
checked srfi-1 and picked funcs to imple.
	modified:   broom/core.brm
	modified:   tests/core_test.brm