static params: expr[T] is now static[T]

This introduces tyStatic and successfully bootstraps and handles
few simple test cases.  Static params within macros are no longer
treated as PNimrodNodes - they are now equivalent to constants
of the designated type.

compiler/evalffi.nim

@@ -78,7 +78,7 @@ proc mapType(t: ast.PType): ptr libffi.TType =
   of tyFloat, tyFloat64: result = addr libffi.type_double
   of tyFloat32: result = addr libffi.type_float
   of tyVar, tyPointer, tyPtr, tyRef, tyCString, tySequence, tyString, tyExpr,
-     tyStmt, tyTypeDesc, tyProc, tyArray, tyArrayConstr, tyNil:
+     tyStmt, tyTypeDesc, tyProc, tyArray, tyArrayConstr, tyStatic, tyNil:
     result = addr libffi.type_pointer
   of tyDistinct:
     result = mapType(t.sons[0])