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/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 368c46d..15f18aa 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -35,8 +35,7 @@
 
 #include "private/bionic_ssp.h"
 #include "private/bionic_tls.h"
-#include "private/debug_format.h"
-#include "private/logd.h"
+#include "private/libc_logging.h"
 #include "private/thread_private.h"
 #include "private/ErrnoRestorer.h"
 #include "private/ScopedPthreadMutexLocker.h"