Use extern C guards in all headers

The project uses a mix of C and C++ requiring
extern "C" guards from C++ code both within the
project & from C++ apps that use libcper. That
won't be required with this change.

Change-Id: I835dd05166732ca213c72eae2904815a8769599b
Signed-off-by: Karthik Rajagopalan <krajagopalan@nvidia.com>
diff --git a/generator/gen-utils.h b/generator/gen-utils.h
index 0ed28c2..1228253 100644
--- a/generator/gen-utils.h
+++ b/generator/gen-utils.h
@@ -1,5 +1,9 @@
-#ifndef GEN_UTILS_H
-#define GEN_UTILS_H
+#ifndef CPER_GEN_UTILS_H
+#define CPER_GEN_UTILS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 #include <stdlib.h>
 #include "../edk/BaseTypes.h"
@@ -18,4 +22,8 @@
 void create_valid_error_section(UINT8 *start);
 UINT8 int_to_bcd(int value);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif