Convert Preserve to simple capture pattern

src/syndicate/patterns.nim

@@ -81,6 +81,7 @@ proc `?`*(T: static typedesc): Pattern =
   ## general case will return a wildcard binding.
   when T is ref:
     ?pointerBase(T)
+  elif T is Preserve: grab()
   elif T.hasCustomPragma(preservesRecord):
     var
       label = tosymbol(T.getCustomPragmaVal(preservesRecord), Ref)