Auto neighbor solicitation is no longer EXPERIMENTAL and is the default for the DK-TM4C129X/ipv6 configuration

ICMPv6: Adds basic logic to support verification that we have the IPv6 address in the Neighbor Table.  This feature is important because otherwise the first packet sent to a remote peer will fail (it will be replaced with a Neighbor Solicitation).

IPv6: More framework for automatic neighbor solicition.  I think this also corrects and error in a broadcast/multicast address chedk

IPv6: Remove an unusd file (kruft from original IPv6 develoment); Add inital hooks to support automatic Neighbor Solitication

Unix domain:  Enable logic to clean up the FIFOs underlying stream sockets with those sockets are disconnected.  Tehre is still no corresponding clean-up logic in place for Unix domain datagram sockets because the life of the FIFO is not as well known in that case

drivers/ramdisk.c and include/nuttx/fs/ramdisk.h:  Add logic to dispose of the drvier and RAM buffer when the RAM disk has been unlinked and all open references to the RAM disk have been closed.  Add new parameters to romdisk() to specify what should be done with the RAM/ROM buffer -- Should it be freed or not?  Changed all calls to ramdisk() to use these new parameters.

Moteino Mega:  Rename files to conform to newer standards.  Need to fix all of the old configurations someday

Add an unlink method to block driver interface.  Same motivataion as for the same modification to the character driver interface

Pipes/FIFOs:  Implement the unlink method.  If the pipe/FIFO is unlinked, it will marked the pipe/FIFO as unliked.  If/when all open references to the driver are closed, all of the driver resources will be freed.

VFS:  Add an unlink method to the character driver interface.  This is important because if the character driver inode is unlinked and there are no open references to the driver, then the driver resources will be stranded.  On the unlink call, the driver has the opportunity (1) check if there an any open references, and (2) if not free the driver resources