preparations for making 'closure' the default calling convention for proc types

lib/system/gc.nim

@@ -45,7 +45,7 @@ type
   TWalkOp = enum
     waZctDecRef, waPush, waCycleDecRef
 
-  TFinalizer {.compilerproc.} = proc (self: pointer)
+  TFinalizer {.compilerproc.} = proc (self: pointer) {.nimcall.}
     # A ref type can have a finalizer that is called before the object's
     # storage is freed.
 

lib/system/hti.nim

@@ -62,7 +62,7 @@ type # This should be he same as ast.TTypeKind
     base: ptr TNimType
     node: ptr TNimNode # valid for tyRecord, tyObject, tyTuple, tyEnum
     finalizer: pointer # the finalizer for the type
-    marker: proc (p: pointer, op: int) # marker proc for GC
+    marker: proc (p: pointer, op: int) {.nimcall.} # marker proc for GC
   PNimType = ptr TNimType
   
 # node.len may be the ``first`` element of a set

lib/system/threads.nim

@@ -255,9 +255,9 @@ type
                           ## that **must not** be part of a message! Use
                           ## a ``TThreadId`` for that.
     when TArg is void:
-      dataFn: proc ()
+      dataFn: proc () {.nimcall.}
     else:
-      dataFn: proc (m: TArg)
+      dataFn: proc (m: TArg) {.nimcall.}
       data: TArg
   TThreadId*[TArg] = ptr TThread[TArg] ## the current implementation uses
                                        ## a pointer as a thread ID.