gethostname() should not be the system call, uname() should and gethostname should get the host name from uname

get/sethostname:  Add a critical section.  There is a microscopic possibily that the global name could change while being accessed by a thread

uname: version string must hold 40 character value; strings returned by uname must always be NUL terminated

SAMD21: Last fix to header files caused a compile problem because logic used a value which is no longer available for the SAMD21

Add support for a BOARDIOC_RESET boardctl() command.  Enable configuration options to support BOARDIOC_RESET for ARMv6-M and ARMv7-M

Simulatin:  Save the intial terminal mode and restore this before terminating.  Otherwise, the NSH shutdown command leaves the console in raw mode

sim configuration: Add support for board_app_initialize() which is needed when CONFIG_LIB_BOARDCTL=y