Clean up ill-advised or unusual header guards

Leading underscores are ill-advised because such identifiers are
reserved.  Trailing underscores are merely ugly.  Strip both.

Our header guards commonly end in _H.  Normalize the exceptions.

Done with scripts/clean-header-guards.pl.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190315145123.28030-7-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
[Changes to slirp/ dropped, as we're about to spin it off]
diff --git a/block/crypto.h b/block/crypto.h
index dd7d479..b935695 100644
--- a/block/crypto.h
+++ b/block/crypto.h
@@ -18,8 +18,8 @@
  *
  */
 
-#ifndef BLOCK_CRYPTO_H__
-#define BLOCK_CRYPTO_H__
+#ifndef BLOCK_CRYPTO_H
+#define BLOCK_CRYPTO_H
 
 #define BLOCK_CRYPTO_OPT_DEF_KEY_SECRET(prefix, helpstr)                \
     {                                                                   \
@@ -94,4 +94,4 @@
 QCryptoBlockOpenOptions *
 block_crypto_open_opts_init(QDict *opts, Error **errp);
 
-#endif /* BLOCK_CRYPTO_H__ */
+#endif /* BLOCK_CRYPTO_H */