NSH: Fix compile issue from all of the recent NETDB changes.  If NETDB is not enabled, we need to use inet_pton() instead of gethostbyname()

apps/examples/nxlines:  Clear a slightly larger rectangle than the one that we drew.  This eliminates edge effects due to applying anti-aliasing twice:  Once when the line was drawn, and again when the line was erased by overwriting it with the background color

apps/netutils/netlib and other files: Create netlib wrapper functions around dns_getserver() and dns_setserver() to isolate application code from changes to those interfaces.

If NSH or Webclient is selected, make sure that CONFIG_LIBC_NETDB is enabled; reanem dnsclient.h to dns.h

apps/netuils/dnsclient and include/netutils/dnsclient.h:  Move the DNS client logic into the NuttX C library.  It is a necessary part for the full implementation of the netdb logic and provides more flexibility in that location.

Print host aliases too; Change how host name is print; the match might be on a host name alias rather than the actual host name

The NSH shutdown option should be called --reboot, not --reset, for compatibility with the statndard shutdown command

system/poweroff:  Use prototype for board_power_off() from include/nuttx/board.h, not from non-supported power.h header file