remove more global variables in the Nim compiler

compiler/ropes.nim

@@ -56,7 +56,7 @@
 #  To cache them they are inserted in a `cache` array.
 
 import
-  platform, hashes
+  hashes
 
 type
   FormatStr* = string  # later we may change it to CString for better
@@ -70,8 +70,6 @@ type
     length*: int
     data*: string             # != nil if a leaf
 
-  RopeSeq* = seq[Rope]
-
 proc len*(a: Rope): int =
   ## the rope's length
   if a == nil: result = 0
@@ -93,7 +91,7 @@ proc freezeMutableRope*(r: Rope) {.inline.} =
   r.length = r.data.len
 
 var
-  cache: array[0..2048*2 - 1, Rope]
+  cache: array[0..2048*2 - 1, Rope] # XXX Global here!
 
 proc resetRopeCache* =
   for i in low(cache)..high(cache):