Make klog_fd thread-safe and make klog_init a no-op.

I'll come back and remove klog_init when I've removed other calls to it.

Change-Id: Iad7fd26d853b4ddc54e9abd44516b6f138cbbfcb
Test: booted N9, looked at "adb shell dmesg" output.
diff --git a/libcutils/Android.mk b/libcutils/Android.mk
index e29c9ad..c830182 100644
--- a/libcutils/Android.mk
+++ b/libcutils/Android.mk
@@ -95,7 +95,7 @@
         android_reboot.c \
         ashmem-dev.c \
         debugger.c \
-        klog.c \
+        klog.cpp \
         partition_utils.c \
         properties.c \
         qtaguid.c \