graphics/traveler:  Restore most of what was removed in the previous commit.  That non-standard logic is currently needed by the simulation.  It should be replaced with use of a framebuffer driver.

netutils/ftpc:  Fix some crazy comparisons to determine is a file is an absolute path.  Noted by Anthony Merlino.

examples/ostest: Extend cancellation test to make sure that cancelable threads waiting on a message queue or on a signal can be canceled.

examples/ostest:  Works around a bug in printf() when cancellation points are enabled.  printf() is a cancellation point because it calls write().  This is correct according to OpenGroup.org.  However, printf holds the stdio library semaphore when it is canceled and this leaves the semaphore in a bad state.  No fix for the printf bug yet.

Add powerled driver example

Approved-by: Gregory Nutt <gnutt@nuttx.org>

examples/elf and nxff: Won't build with CONFIG_BUILD_KERNEL because the interface exec() is not available in that configuration.  Also, remove a stray comma and a stray semacolon in examples/pty_test/Kconfig and examples/random/Kconfig

apps/examples:  In elf and nxflat examples, remove low-level interfaces and replace with call to exec().

apps/examples/flowc: Fix some errors in receiver's verificationg logic.  Add a 'canned' data file so that we don't need to deal with the sender program; we can just 'cat' the canned data file.

nshlib/nsh_netcmds.c: Fix a compilation error when IPv4/IPv6 dual stack is enabled

Approved-by: Gregory Nutt <gnutt@nuttx.org>

    nshlib/nsh_parse.c: Avoid truncating the strcmp result into a unsigned char variable.

    nshlib/nsh_netcmds.c: Check for valid hostip before using it.

    nshlib/nsh_ddcmd.c: Fix resouce leak when 'if=' or 'of=' params are repeated in the command line.  For example:

       dd if=/dev/null if=/dev/zero of=/dev/null or
       dd if=/dev/zero of=/dev/zero of=/dev/null

    apps/examples/flowc:  Adds the necessary termios controls to enable hardware flow control

    apps/examples/flowc:  Add a simple test of serial hardware flow control.  This commit just defines the frame work.  Hardware flow control is not yet enabled.