Add load base to map for relocation packing.

The new linker relocation packing support uses non-zero load bases,
so we better handle them properly.

Also print out the load base for a map if it's non-zero.

Bug: 20687795
Change-Id: Iec2d1db2051e7b4a278c1dfa57d745128a7f2974
diff --git a/libbacktrace/UnwindMap.cpp b/libbacktrace/UnwindMap.cpp
index fa59d07..4a4e2f3 100644
--- a/libbacktrace/UnwindMap.cpp
+++ b/libbacktrace/UnwindMap.cpp
@@ -51,6 +51,7 @@
 
     map.start = unw_map.start;
     map.end = unw_map.end;
+    map.load_base = unw_map.load_base;
     map.flags = unw_map.flags;
     map.name = unw_map.path;
 
@@ -91,6 +92,7 @@
 
       map.start = unw_map.start;
       map.end = unw_map.end;
+      map.load_base = unw_map.load_base;
       map.flags = unw_map.flags;
       map.name = unw_map.path;