Move string functions to libstring

libstring/string.h

@@ -0,0 +1,13 @@
+#ifndef _LIBSTRING_STRING_H
+#define _LIBSTRING_STRING_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+size_t memset (void* dst, uint8_t b, size_t n);
+size_t memcpy (void* dst, const void* src, size_t n);
+void strncpy (char* dst, const char* src, size_t n);
+size_t strlen (const char* str);
+int memcmp (const void* s1, const void* s2, size_t n);
+
+#endif // _LIBSTRING_STRING_H