Remove top-level unquote for comptime macro

True top level unquote currently requires basically double compilation
as it currently stands. Also, implementing such double compilation
looses all source mapping information. This is a compromise
implementation that makes it clear that this works differently than
a true top-level unquote.

src/boot/boot.janet

@@ -1850,9 +1850,9 @@
     (res)
     (error (res :error))))
 
-(def unquote
-  "(unquote x)\n\nEscapes one level inside of a quasiquote. When used outside of a quasiquote, evaluates
-  its argument at compile-time."
+(def comptime
+  "(comptime x)\n\n
+  Evals x at compile time and returns the result. Similar to a top level unquote."
   :macro eval)
 
 (defn make-image

src/core/specials.c

@@ -120,6 +120,13 @@ static JanetSlot janetc_quasiquote(JanetFopts opts, int32_t argn, const Janet *a
     return quasiquote(opts, argv[0], JANET_RECURSION_GUARD, 0);
 }
 
+static JanetSlot janetc_unquote(JanetFopts opts, int32_t argn, const Janet *argv) {
+    (void) argn;
+    (void) argv;
+    janetc_cerror(opts.compiler, "cannot use unquote here");
+    return janetc_cslot(janet_wrap_nil());
+}
+
 /* Perform destructuring. Be careful to
  * keep the order registers are freed.
  * Returns if the slot 'right' can be freed. */
@@ -812,6 +819,7 @@ static const JanetSpecial janetc_specials[] = {
     {"quote", janetc_quote},
     {"set", janetc_varset},
     {"splice", janetc_splice},
+    {"unquote", janetc_unquote},
     {"var", janetc_var},
     {"while", janetc_while}
 };

test/suite7.janet

@@ -273,8 +273,8 @@
 # Top level unquote
 (defn constantly
   []
-  ,(math/random))
+  (comptime (math/random)))
 
-(assert (= (constantly) (constantly)) "top level unquote")
+(assert (= (constantly) (constantly)) "comptime 1")
 
 (end-suite)