Clean up nre imports

lib/impure/nre.nim

@@ -7,11 +7,10 @@
 #
 
 
-import pcre as pcre
+from pcre import nil
 import nre.private.util
 import tables
 import unsigned
-from future import lc, `[]`
 from strutils import toLower, `%`
 from math import ceil
 import options