The sendmail example hasn't been used in years. I am not sure it was ever debugged. It is so old that it still expects hand editted .config files. As a result, all of the configuration settings were missing from the Kconfig file.
This commit adds the missing apps/examples/sendmail configuration settings so that the example at least builds. I cannot test it because I have no smtp server that I am willing to spam.
This configuration also adds missing configuration dependencies and runs the C files in apps/examples/sendmail and apps/netutils/smtp through nxstyle.
This commit resolves an issue reported by surya prakash rased in the Google group: https://groups.google.com/forum/#!topic/nuttx/idr-M164Y24
