Minor fixes to enable tcc

config/nim.cfg

@@ -118,7 +118,7 @@ path="$lib/pure"
 # Configuration for the GNU C/C++ compiler:
 @if windows:
   #gcc.path = r"$nim\dist\mingw\bin"
-  @if gcc:
+  @if gcc or tcc:
     tlsEmulation:on
   @end
 @end

lib/pure/concurrency/threadpool.nim

@@ -331,7 +331,7 @@ proc slave(w: ptr Worker) {.thread.} =
     await(w.taskArrived)
     # XXX Somebody needs to look into this (why does this assertion fail
     # in Visual Studio?)
-    when not defined(vcc): assert(not w.ready)
+    when not defined(vcc) and not defined(tcc): assert(not w.ready)
 
     withLock numSlavesLock:
       inc numSlavesRunning

lib/system/atomics.nim

@@ -241,7 +241,7 @@ when defined(vcc):
     else:
       {.error: "invalid CAS instruction".}
 
-elif defined(tcc) and not defined(windows):
+elif defined(tcc):
   when defined(amd64):
     {.emit:"""
 static int __tcc_cas(int *ptr, int oldVal, int newVal)
@@ -262,7 +262,7 @@ static int __tcc_cas(int *ptr, int oldVal, int newVal)
 }
 """.}
   else:
-    assert sizeof(int) == 4
+    #assert sizeof(int) == 4
     {.emit:"""
 static int __tcc_cas(int *ptr, int oldVal, int newVal)
 {