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/setjmp.h

@@ -0,0 +1,27 @@
+/*
+	setjmp.h
+	stubs for future use.
+*/
+
+#ifndef _SETJMP_H_
+#define _SETJMP_H_
+
+#include "_ansi.h"
+#include <machine/setjmp.h>
+
+_BEGIN_STD_C
+
+#ifdef __GNUC__
+void	_EXFUN(longjmp,(jmp_buf __jmpb, int __retval))
+			__attribute__ ((__noreturn__));
+#else
+void	_EXFUN(longjmp,(jmp_buf __jmpb, int __retval));
+#endif
+int	_EXFUN(setjmp,(jmp_buf __jmpb));
+#define setjmp(env) setjmp(env)
+
+
+_END_STD_C
+
+#endif /* _SETJMP_H_ */
+