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/malloc_debug_common.h b/libc/bionic/malloc_debug_common.h
index e15ccd0..12d0e65 100644
--- a/libc/bionic/malloc_debug_common.h
+++ b/libc/bionic/malloc_debug_common.h
@@ -35,7 +35,7 @@
 
 #include <stdlib.h>
 
-#include <private/debug_format.h>
+#include "libc_logging.h"
 
 #define HASHTABLE_SIZE      1543
 #define BACKTRACE_SIZE      32