cmdline: renamed options.stderr to options.log_stderr

On FreeBSD, "stderr" is a macro, and using this name for a struct
member breaks the build.

[mk: renamed _stderr to log_stderr]

src/cmdline.h

@@ -25,7 +25,7 @@
 struct options {
 	gboolean kill;
 	gboolean daemon;
-	gboolean stderr;
+	gboolean log_stderr;
 	gboolean verbose;
 	int create_db;
 };