[parseopt] Add support for boolean options

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/parseopt.c

 	return 0;
 }
 
+/**
+ * Parse flag
+ *
+ * @v text		Text (ignored)
+ * @ret flag		Flag to set
+ * @ret rc		Return status code
+ */
+int parse_flag ( const char *text __unused, int *flag ) {
+
+	/* Set flag */
+	*flag = 1;
+
+	return 0;
+}
+
 /**
  * Print command usage message
  *

src/include/ipxe/parseopt.h

 extern int parse_integer ( const char *text, unsigned int *value );
 extern int parse_netdev ( const char *text, struct net_device **netdev );
 extern int parse_image ( const char *text, struct image **image );
+extern int parse_flag ( const char *text __unused, int *flag );
 extern void print_usage ( struct command_descriptor *cmd, char **argv );
 extern int parse_options ( int argc, char **argv,
 			   struct command_descriptor *cmd, void *opts );