Fix a few deprecation warnings

tests/threads/threadex.nim

@@ -11,7 +11,7 @@ type
     of mLine: data: string
 
 var
-  producer, consumer: TThread[void]
+  producer, consumer: Thread[void]
   chan: TChannel[TMsg]
   printedLines = 0
 

tests/threads/tthreadanalysis.nim

@@ -8,7 +8,7 @@ discard """
 import os
 
 var
-  thr: array [0..5, TThread[tuple[a, b: int]]]
+  thr: array [0..5, Thread[tuple[a, b: int]]]
 
 proc doNothing() = discard
 

tests/threads/tthreadanalysis2.nim

@@ -8,7 +8,7 @@ discard """
 import os
 
 var
-  thr: array [0..5, TThread[tuple[a, b: int]]]
+  thr: array [0..5, Thread[tuple[a, b: int]]]
 
 proc doNothing() = discard
 

tests/threads/tthreadheapviolation1.nim

@@ -6,7 +6,7 @@ discard """
 
 var
   global: string = "test string"
-  t: TThread[void]
+  t: Thread[void]
 
 proc horrible() {.thread.} =
   global = "string in thread local heap!"

tests/threads/ttryrecv.nim

@@ -15,7 +15,7 @@ proc doAction(outC: PComm) {.thread.} =
     send(outC[], i)
 
 var
-  thr: TThread[PComm]
+  thr: Thread[PComm]
   chan: TChannel[int]
 
 open(chan)