RT2308: Add extern "C" { ... } wrapper

Add the wrapper to all public header files (Configure
generates one).  Don't bother for those that are just
lists of #define's that do renaming.

Reviewed-by: Tim Hudson <tjh@openssl.org>

Cherry-pick of commit 17e80c6bd0

crypto/modes/modes.h

@@ -7,6 +7,9 @@
 
 #include <stddef.h>
 
+#ifdef  __cplusplus
+extern "C" {
+#endif
 typedef void (*block128_f)(const unsigned char in[16],
 			unsigned char out[16],
 			const void *key);
@@ -141,3 +144,6 @@ size_t CRYPTO_128_wrap(void *key, const unsigned char *iv,
 size_t CRYPTO_128_unwrap(void *key, const unsigned char *iv,
 		unsigned char *out,
 		const unsigned char *in, size_t inlen, block128_f block);
+#ifdef  __cplusplus
+}
+#endif