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/tests/base64_test.cpp b/tests/base64_test.cpp
index b762b8e..3fcb3af 100644
--- a/tests/base64_test.cpp
+++ b/tests/base64_test.cpp
@@ -1,6 +1,4 @@
-extern "C" {
 #include "base64.h"
-}
 
 #include "gtest/gtest.h"
 #include "gmock/gmock.h"
diff --git a/tests/ir-tests.cpp b/tests/ir-tests.cpp
index e8db79f..061f0a8 100644
--- a/tests/ir-tests.cpp
+++ b/tests/ir-tests.cpp
@@ -7,14 +7,12 @@
 #include <cctype>
 #include "gtest/gtest.h"
 #include "test-utils.hpp"
-extern "C" {
 #include <json.h>
 #include "../cper-parse.h"
 #include "../json-schema.h"
 #include "../generator/cper-generate.h"
 #include "../sections/cper-section.h"
 #include "../generator/sections/gen-section.h"
-}
 
 /*
 * Test templates.
diff --git a/tests/test-utils.cpp b/tests/test-utils.cpp
index 3837030..53aecd3 100644
--- a/tests/test-utils.cpp
+++ b/tests/test-utils.cpp
@@ -7,10 +7,9 @@
 #include <cstdio>
 #include <cstdlib>
 #include "test-utils.hpp"
-extern "C" {
+
 #include "../edk/BaseTypes.h"
 #include "../generator/cper-generate.h"
-}
 
 //Returns a ready-for-use memory stream containing a CPER record with the given sections inside.
 FILE *generate_record_memstream(const char **types, UINT16 num_types,