OS test: Mark some constants as long to avoid overflow when used the AVR8.  Example, 500*1000 overflows when type int is only 16-bits, but 500*1000L avoids the overflow

OS test:  Add a test of POSIX timers using SIGEV_THREAD.  Also, clean up many warnings with building on a PC with 64-bit addresses

apps/examples/pca9635:  Add a simple test of PCA9635PW PWM LED driver.  From Alan Carvalho de Assis.

apps/netutils/ping:  This is an unfinished implementation of ping/ping6 using raw packets.  Not yet even hooked into the build and configuration systems

netutils/telnetd:  No longer calls OS interfade telnet_driver.  Now creates Telnet sessions by open a new factory device at /dev/telnet and then using ioctl calls to create the session character drivers at /dev/telnetN.

NSH DD command:  Use nsh_freefullpath() instead of free().  Actually, these are the so this does not fix bug.  It is just needed for symmetry.

apps/nshlib:  The 'ps' command now uses /proc/(pid)/ to obtain task status information.  A consequence of this is that you cannot use the 'ps' command if the procfs is not enabled and mounted at /proc.