Add curenv to core.

CHANGELOG.md

@@ -2,6 +2,7 @@
 All notable changes to this project will be documented in this file.
 
 ## Unreleased - ???
+- Add `(curenv)`.
 - Change `net/read`, `net/chunk`, and `net/write` to raise errors in the case of failures.
 - Add `janet_continue_signal` to C API. This indirectly enables C functions that yield to the event loop
   to raise errors or other signals.

src/boot/boot.janet

@@ -2069,6 +2069,14 @@
       (if ec "\e[0m" "")))
   (eflush))
 
+(defn curenv
+  "Get the current environment table. Same as (fiber/getenv (fiber/current)). If n
+  is provided, gets the nth prototype of the environment table."
+  [&opt n]
+  (var e (fiber/getenv (fiber/current)))
+  (if n (repeat n (if (= nil e) (break)) (set e (table/getproto e))))
+  e)
+
 (defn run-context
   "Run a context. This evaluates expressions in an environment,
   and is encapsulates the parsing, compilation, and evaluation.