Add :export option to import

Also allow NULL ptr to janet_getfile for flags.

src/core/core.janet

@@ -1687,18 +1687,20 @@ value, one key will be ignored."
   table."
   [env path & args]
   (def {:as as
-        :prefix prefix} (table ;args))
+        :prefix prefix
+        :export ep} (table ;args))
   (def newenv (require path ;args))
   (def prefix (or (and as (string as "/")) prefix (string path "/")))
   (loop [[k v] :pairs newenv :when (not (v :private))]
-    (def newv (table/setproto @{:private true} v))
+    (def newv (table/setproto @{:private (not ep)} v))
     (put env (symbol prefix k) newv)))
 
 (defmacro import
   "Import a module. First requires the module, and then merges its
   symbols into the current environment, prepending a given prefix as needed.
   (use the :as or :prefix option to set a prefix). If no prefix is provided,
-  use the name of the module as a prefix."
+  use the name of the module as a prefix. One can also use :export true
+  to re-export the imported symbols."
   [path & args]
   (def argm (map (fn [x]
                    (if (keyword? x)

src/core/io.c

@@ -404,7 +404,7 @@ static const JanetReg io_cfuns[] = {
 
 FILE *janet_getfile(const Janet *argv, int32_t n, int *flags) {
     IOFile *iof = janet_getabstract(argv, n, &cfun_io_filetype);
-    *flags = iof->flags;
+    if (NULL != flags) *flags = iof->flags;
     return iof->file;
 }
 

src/include/janet.h

@@ -1256,7 +1256,6 @@ JANET_API int32_t janet_getargindex(const Janet *argv, int32_t n, int32_t length
 
 JANET_API FILE *janet_getfile(const Janet *argv, int32_t n, int *flags);
 
-
 /* Marshal API */
 JANET_API void janet_marshal_int(JanetMarshalContext *ctx, int32_t value);
 JANET_API void janet_marshal_byte(JanetMarshalContext *ctx, uint8_t value);