Many changes for adding dynamic (fiber-level) scope.

- Allow passing a table to fibers, which make fiber level scope easier.
- Add fiber/getenv, fiber/setenv, dyn, and setdyn
- Remove meta, *env*, and *doc-width*
- Some functions changed dignatures, and no longer take an env

test/suite1.janet

@@ -140,7 +140,7 @@
 
 # Marshal
 
-(def um-lookup (env-lookup *env*))
+(def um-lookup (env-lookup (fiber/getenv (fiber/current))))
 (def m-lookup (invert um-lookup))
 
 (defn testmarsh [x msg]
@@ -182,7 +182,7 @@
 # Large functions
 (def manydefs (seq [i :range [0 300]] (tuple 'def (gensym) (string "value_" i))))
 (array/push manydefs (tuple * 10000 3 5 7 9))
-(def f (compile ['do ;manydefs] *env*))
+(def f (compile ['do ;manydefs] (fiber/getenv (fiber/current))))
 (assert (= (f) (* 10000 3 5 7 9)) "long function compilation")
 
 # Some higher order functions and macros