Provide our own newlib libc

Newlib 2.2.0 w/ nan ofeatures, xtensa patches, locking
implementation.

Built from https://github.com/projectgus/newlib-xtensa
branch xtensa-2_2_0-lock
commit daa6ae40cdc8099f54c3e68a586fc1b906169c5a

For more details, see:
https://github.com/SuperHouse/esp-open-rtos/wiki/libc-configuration

Closes #1

libc/xtensa-lx106-elf/include/dirent.h

@@ -0,0 +1,15 @@
+#ifndef _DIRENT_H_
+#define _DIRENT_H_
+#ifdef __cplusplus
+extern "C" {
+#endif
+#include <sys/dirent.h>
+
+#if !defined(MAXNAMLEN) && !defined(_POSIX_SOURCE)
+#define MAXNAMLEN 1024
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+#endif /*_DIRENT_H_*/