use ftpsrv config and mountpoints, improve ftp performance by using its vfs.

sphaira/include/log.hpp

@@ -2,12 +2,15 @@
 
 #define sphaira_USE_LOG 1
 
+#include <cstdarg>
+
 #if sphaira_USE_LOG
 auto log_file_init() -> bool;
 auto log_nxlink_init() -> bool;
 void log_file_exit();
 void log_nxlink_exit();
 void log_write(const char* s, ...) __attribute__ ((format (printf, 1, 2)));
+void log_write_arg(const char* s, std::va_list& v);
 #else
 inline auto log_file_init() -> bool {
     return true;