[lib][cbuf] C++ header guard the cbuf header

lib/cbuf/include/lib/cbuf.h

@@ -22,11 +22,14 @@
  */
 #pragma once
 
+#include <compiler.h>
 #include <sys/types.h>
 #include <kernel/event.h>
 #include <kernel/spinlock.h>
 #include <iovec.h>
 
+__BEGIN_CDECLS
+
 typedef struct cbuf {
     uint head;
     uint tail;
@@ -157,3 +160,5 @@ static inline void cbuf_reset(cbuf_t *cbuf)
 size_t cbuf_read_char(cbuf_t *cbuf, char *c, bool block);
 size_t cbuf_write_char(cbuf_t *cbuf, char c, bool canreschedule);
 
+__END_CDECLS
+