reference implementation of a vector swizzle library

This also provides the initial steps towards support for type class "filtered" type inference
fixes an "ordinal type expected" ICE, related to the use of static params

compiler/ast.nim

@@ -435,6 +435,8 @@ type
     tfUnresolved,     # marks unresolved typedesc/static params: e.g.
                       # proc foo(T: typedesc, list: seq[T]): var T
                       # proc foo(L: static[int]): array[L, int]
+                      # can be attached to ranges to indicate that the range
+                      # depends on unresolved static params.
     tfRetType,        # marks return types in proc (used to detect type classes 
                       # used as return types for return type inference)
     tfCapturesEnv,    # whether proc really captures some environment