Fix an off-by-one error when releasing thread ids.  This is the result
of an oversight in my change that eliminated the LSB set constraint on
assigned thread ids.
diff --git a/vm/Thread.c b/vm/Thread.c
index e26e679..7505ec5 100644
--- a/vm/Thread.c
+++ b/vm/Thread.c
@@ -1216,7 +1216,7 @@
 static void releaseThreadId(Thread* thread)
 {
     assert(thread->threadId > 0);
-    dvmClearBit(gDvm.threadIdMap, (thread->threadId >> 1) - 1);
+    dvmClearBit(gDvm.threadIdMap, thread->threadId - 1);
     thread->threadId = 0;
 }