How to avoid deprecation notice for libraies supporting multi-version of Nim?

[jackhftang]

Did you import from another file? I tested on three machines with the following 
settings, all showing `undeclared identifier: 'tables'`.

Here the codes, two files or clone `git clone 
https://github.com/jackhftang/lrucache.nim.git -b minimal_rightsize_test`
    
    
    # lrucache.nim
    import lists
    import tables
    
    type
      # no need to use ref, since DoublyLinkedNode is already a ref
      Node[K,T] = object
        key: K
        val: T
      
      LruCache*[K, T] = ref object
        capacity: int
        list: DoublyLinkedList[Node[K,T]]
        table: Table[K, DoublyLinkedNode[Node[K,T]]]
    
    template rightSize(cap): untyped {.dirty.} =
      when (NimMajor,NimMinor)<(1,4):
        tables.rightSize(cap)
      else:
        cap
    
    proc newLruCache*[K,T](capacity: int): LruCache[K,T] =
      ## Create a new Least-Recently-Used (LRU) cache that store the last 
`capacity`-accessed items.
      LruCache[K,T](
        capacity: capacity,
        list: initDoublyLinkedList[Node[K,T]](),
        table: initTable[K, DoublyLinkedNode[Node[K,T]]]( rightSize(capacity) )
      )
    
    
    Run
    
    
    # test.nim
    import lrucache
    
    let c = newLruCache[int,int](10)
    
    
    Run

run with `nim c -r test.nim`

I do not know why tables is not defined, also I cannot see what wrong I did in 
the code. Let me know If you still cannot reproduce it. I don't think my nim 
setup has anything special.

tested on

  * windows nim-1.2.0 installed from tarball
  * linux: choosnim 1.2.6
  * linux: choosnim 1.2.4
  * linux: choosnim 1.0.0
  * osx: choosnim 1.2.6
  * osx: choosnim 1.0.0