Move CallStack to libbacktrace.

Fix a small bug in the Printer for strings that didn't properly
prepend the prefix.

(cherry picked from commit 9b0e074c6d38143e01616404a08b0c7aa992f3c3)

Change-Id: I78bfa3f76864c34f33fb439bf20dfc85616f1077
diff --git a/include/utils/ProcessCallStack.h b/include/utils/ProcessCallStack.h
index 4a86869..32458b8 100644
--- a/include/utils/ProcessCallStack.h
+++ b/include/utils/ProcessCallStack.h
@@ -39,7 +39,7 @@
     ~ProcessCallStack();
 
     // Immediately collect the stack traces for all threads.
-    void update(int32_t maxDepth = CallStack::MAX_DEPTH);
+    void update();
 
     // Print all stack traces to the log using the supplied logtag.
     void log(const char* logtag, android_LogPriority priority = ANDROID_LOG_DEBUG,