Move map data into backtrace data proper.

The backtrace structure used to include a pointer to a backtrace_map_t
that represented the map data for a particular pc. This introduced a
race condition where the pointer could be discarded, but the backtrace
structure still contained a pointer to garbage memory. Now all of the map
information is right in the structure.

Bug: 19028453
Change-Id: If7088a73f3c6bf1f3bc8cdd2bb4b62e7cab831c0
diff --git a/libbacktrace/UnwindPtrace.cpp b/libbacktrace/UnwindPtrace.cpp
index 7ba8775..efe758b 100644
--- a/libbacktrace/UnwindPtrace.cpp
+++ b/libbacktrace/UnwindPtrace.cpp
@@ -106,7 +106,7 @@
 
       frame->func_name = GetFunctionName(frame->pc, &frame->func_offset);
 
-      frame->map = FindMap(frame->pc);
+      FillInMap(frame->pc, &frame->map);
 
       num_frames++;
     } else {