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/cper-generate.h b/generator/cper-generate.h
index edbac36..042431f 100644
--- a/generator/cper-generate.h
+++ b/generator/cper-generate.h
@@ -1,10 +1,18 @@
 #ifndef CPER_GENERATE_H
 #define CPER_GENERATE_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stdio.h>
 #include "../edk/BaseTypes.h"
 
 void generate_cper_record(char **types, UINT16 num_sections, FILE *out);
 void generate_single_section_record(char *type, FILE *out);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif