Define m_secmarker_skipped as an integer type

There's no reason to treat this this as a double, since it
represents a human-readable data value that is only meaningful
as an integer. In doing so we write cleaner audit logs and save
a small amount of space.

test/test-cases/regression/secmarker.json

@@ -110,7 +110,7 @@
     },
     "expected": {
       "audit_log": "",
-      "debug_log": "Out of a SecMarker after skip 6.000000 rules.",
+      "debug_log": "Out of a SecMarker after skip 6 rules.",
       "error_log": ""
     },
     "rules": [