degesch: add static analysis for the logger

Caught two more occurences than I was able to find by just scanning
the source, so the effort wasn't in vain.

test-static

@@ -0,0 +1,14 @@
+#!/bin/sh
+# We don't use printf's percent notation with our custom logging mechanism,
+# so the compiler cannot check it for us like it usually does
+perl -n0777 - "$(dirname "$0")"/degesch.c <<-'END'
+	while (/\blog_[^ ]+\s*\([^"()]*"[^"]*%[^%][^"]*"/gm) {
+		my ($p, $m) = ($`, $&);
+		printf "$ARGV:%d: suspicious log format string: %s...\n",
+			(1 + $p =~ tr/\n//), ($m =~ s/\s+/ /rg);
+		$status = 1;
+	}
+	END {
+		exit $status;
+	}
+END