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/netbsd/resolv/res_state.c b/libc/netbsd/resolv/res_state.c
index e05846a..3e1f67b 100644
--- a/libc/netbsd/resolv/res_state.c
+++ b/libc/netbsd/resolv/res_state.c
@@ -42,9 +42,9 @@
 #define DEBUG 0
 
 #if DEBUG
-#  include <logd.h>
+#  include "libc_logging.h"
 #  include <unistd.h>  /* for gettid() */
-#  define D(...)  __libc_android_log_print(ANDROID_LOG_DEBUG,"libc", __VA_ARGS__)
+#  define D(...) __libc_format_log(ANDROID_LOG_DEBUG,"libc", __VA_ARGS__)
 #else
 #  define D(...)  do{}while(0)
 #endif