Add extern "C" to headers

Add extern "C" to headers so that they can be included by cpp code.

Signed-off-by: Deepak Kodihalli <dkodihal@in.ibm.com>
diff --git a/libmctp.h b/libmctp.h
index 28903d7..d1696a4 100644
--- a/libmctp.h
+++ b/libmctp.h
@@ -3,6 +3,10 @@
 #ifndef _LIBMCTP_H
 #define _LIBMCTP_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stdint.h>
 
 typedef uint8_t mctp_eid_t;
@@ -90,4 +94,8 @@
 		void *(realloc)(void *, size_t));
 
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _LIBMCTP_H */