SAMV7 Ethernet:  I- and D-Cache are now enabled in the netnsh/ configuration.  D-Cache is enabled in write-though mode.  This mode is necessary because the DMA descriptors are each 8-bytes in size but the D-Cache cache line is 32-bits in size. So it is impossible make coherency for every 8-byte DMA descriptor without write-through.

Make sure that FPU test, HID keyboard example, and touchscreen options are only available in the FLAT build

Fix two uses of DEBUG_COLORATION vs STACK_COLORATION (from David Sidrane).  Also some corrected comments

Fix some time value changes; mostly changing greater than 1000000000 to greater than or equal to 1000000000.  From Juha Niskanen

apps/examples/ostest: Sample errno on returns from sem_timedwait().  Otherwise, intervening system calls my change the value of the reported errno.  Noted by Juha Niskanen

apps/platform/Makefile:  Add a default defintion for DELIM.  Apparently it may not be present in certain causes during 'make distclean'.  From Michal Ulianko (SourceForge patch #47

NSH: The default priority of the network initialization thread should be lower.  It is CPU intensive and can interfere with other operations

apps/netutils/netlib:  Add utilities to convert to/from prefix lengths from/to 128-bit network masks.  Modify the NSH IPv6 ifconfig command to show the network mask in a more standard, human readable way.

ICMPv6:  Some initial bugfix from first tests of the ICMPv6 auto-configuration logic.  so far so good but a lot more testing is needed

Build-server sometimes fails 'make -j24' with:

 In file included from builtin_list.c:62:0:
 builtin_list.h:1:46: error: 'ts_engine_main' undeclared here (not in a function)
  { "ts_engine", SCHED_PRIORITY_DEFAULT, 2048, ts_engine_main },

or sometimes silently succeeds but generates builds that contain
a random subset of configured NuttX applications. There are two
root causes for this:

1) Recipes for building builtin_list.h and builtin_proto.h are not
   linearizable.
2) Nothing ensures that 'make context' is run first for apps/builtin

This patch addresses both issues.

Signed-off-by: Juha Niskanen <juha.niskanen@haltian.com>

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.

Unix domain/FIFOs:  Fix a race condition between FIFO buffer operations and the opening and closing of FIFOs which necessary when the FIFOs are used to support Unix domain, datagram sockets.  The default policy is the deallocate FIFO buffering when the last client closes the pipe.  When when used for datagram communicatinos, packets left in the FIFO will be lost.  Some like UDP read-ahead is needed:  The buffered data in the FIFO needs to be retained until the reader gets a chance to re-open the FIFO.  Added an ioctl (PIPEIOC_POLICY) to control the buffer policy. Default (0) is the legacy behavior; Unix domain datagram logic sets the alternative policy so that the packet data persists after the FIFO is closed.