Constify data structures

Constify more data structures. Make functions static.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
diff --git a/extensions/libipt_LOG.c b/extensions/libipt_LOG.c
index cf8990a..0f13c24 100644
--- a/extensions/libipt_LOG.c
+++ b/extensions/libipt_LOG.c
@@ -57,7 +57,7 @@
 	unsigned int level;
 };
 
-static struct ipt_log_names ipt_log_names[]
+static const struct ipt_log_names ipt_log_names[]
 = { { .name = "alert",   .level = LOG_ALERT },
     { .name = "crit",    .level = LOG_CRIT },
     { .name = "debug",   .level = LOG_DEBUG },