Fix include guards: No _ prefix/suffix but _H suffix (as in upstream)

src/modules/surjection/surjection_impl.h

@@ -4,8 +4,8 @@
  * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
  **********************************************************************/
 
-#ifndef _SECP256K1_SURJECTION_IMPL_H_
-#define _SECP256K1_SURJECTION_IMPL_H_
+#ifndef SECP256K1_SURJECTION_IMPL_H
+#define SECP256K1_SURJECTION_IMPL_H
 
 #include <assert.h>
 #include <string.h>