Clean up internal libc logging.

We only need one logging API, and I prefer the one that does no
allocation and is thus safe to use in any context.

Also use O_CLOEXEC when opening the /dev/log files.

Move everything logging-related into one header file.

Change-Id: Ic1e3ea8e9b910dc29df351bff6c0aa4db26fbb58
diff --git a/libc/bionic/stubs.cpp b/libc/bionic/stubs.cpp
index 8ddc326..e8411b7 100644
--- a/libc/bionic/stubs.cpp
+++ b/libc/bionic/stubs.cpp
@@ -38,9 +38,8 @@
 #include <unistd.h>
 
 #include "private/android_filesystem_config.h"
-#include "private/debug_format.h"
 #include "private/ErrnoRestorer.h"
-#include "private/logd.h"
+#include "private/libc_logging.h"
 
 // Thread-specific state for the non-reentrant functions.
 static pthread_once_t stubs_once = PTHREAD_ONCE_INIT;