bugfix: fixed memory leaks in osproc module

tests/threads/tactors.nim

@@ -0,0 +1,13 @@
+discard """
+  outputsub: "150"
+"""
+
+import actors
+
+var
+  a: TActorPool[int, void]
+createActorPool(a)
+for i in 0 .. < 300:
+  a.spawn(i, proc (x: int) {.thread.} = echo x)
+a.join()
+

tests/threads/threadex.nim

@@ -1,3 +1,6 @@
+discard """
+  output: ""
+"""
 
 type
   TMsgKind = enum
@@ -18,7 +21,7 @@ proc consume() {.thread.} =
       x.backTo.send(printedLines)
       break
     echo x.data
-    discard atomicInc(printedLines)
+    atomicInc(printedLines)
 
 proc produce() =
   var m: TMsg

tests/threads/tthreadanalysis2.nim

@@ -1,6 +1,6 @@
 discard """
   file: "tthreadanalysis2.nim"
-  line: 45
+  line: 42
   errormsg: "write to foreign heap"
   cmd: "nimrod cc --hints:on --threads:on $# $#"
 """