Shorten thread names

prctl(PR_SET_NAME) limits to 15 characters.  Before we had names like
"Binder Thread #" and the counter was cut off :-( Also remove redundant
"thread" at end of name; it's always a thread.

Change-Id: I1f99c2730ba0787ed9b59c15914356cddf698e2f
diff --git a/libs/binder/ProcessState.cpp b/libs/binder/ProcessState.cpp
index f96fe50..9fa412c 100644
--- a/libs/binder/ProcessState.cpp
+++ b/libs/binder/ProcessState.cpp
@@ -286,8 +286,8 @@
 {
     if (mThreadPoolStarted) {
         int32_t s = android_atomic_add(1, &mThreadPoolSeq);
-        char buf[32];
-        sprintf(buf, "Binder Thread #%d", s);
+        char buf[16];
+        snprintf(buf, sizeof(buf), "Binder_%X", s);
         ALOGV("Spawning new pooled thread, name=%s\n", buf);
         sp<Thread> t = new PoolThread(isMain);
         t->run(buf);