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/sections/gen-section.h b/generator/sections/gen-section.h
index be00b5f..d1987b9 100644
--- a/generator/sections/gen-section.h
+++ b/generator/sections/gen-section.h
@@ -1,6 +1,10 @@
 #ifndef GEN_SECTIONS_H
 #define GEN_SECTIONS_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stdlib.h>
 #include "../../edk/Cper.h"
 
@@ -32,4 +36,8 @@
 extern CPER_GENERATOR_DEFINITION generator_definitions[];
 extern const size_t generator_definitions_len;
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif