Move UpdateStatus and helpers to dedicated files

This allows us to easily share it between the update_engine proper
and a forthcoming client library.

Bug: 24547247
Test: mmm system/update_engine; emerge-panther update_engine

Change-Id: I8c0db7a0f95dd6368bfc886f1b0d1a9d2efb461f
diff --git a/Android.mk b/Android.mk
index abbae26..5962573 100644
--- a/Android.mk
+++ b/Android.mk
@@ -45,6 +45,7 @@
     LOCAL_LDFLAGS += \
         -Wl,--gc-sections
     LOCAL_C_INCLUDES += \
+        $(LOCAL_PATH)/client_library/include \
         external/gtest/include \
         system
     LOCAL_SHARED_LIBRARIES += \
@@ -177,6 +178,7 @@
     update_manager/real_updater_provider.cc \
     update_manager/state_factory.cc \
     update_manager/update_manager.cc \
+    update_status_utils.cc \
     utils.cc \
     xz_extent_writer.cc
 $(eval $(update_engine_common))