cutils: Add tracing support

Basic tracing functionality to cutils, which can be turned on at start,
or dynamically controlled by the frameworks.  The goal is for hardware
modules to add tracing that will be controlled by their respective
services.

Change-Id: I84eeb7d6be0038f734e719074fa4a2fae4ffe9c0
diff --git a/libcutils/Android.mk b/libcutils/Android.mk
index fc6d08d..23a73d2 100644
--- a/libcutils/Android.mk
+++ b/libcutils/Android.mk
@@ -121,6 +121,7 @@
         mq.c \
         partition_utils.c \
         qtaguid.c \
+        trace.c \
         uevent.c
 
 ifeq ($(TARGET_ARCH),arm)