Add support for a login script (in addition to the init script); Add logic so...

Add support for a login script (in addition to the init script); Add logic so that a USB console session can connect and reconnect to the USB serial device

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5582 42af7a65-404d-4744-a932-0658087f49c3