ix an error in time initialization when there is not RTC and the time is initialized from a fixed configured value. The call to clock_calendar2utc() was returning the time in units of seconds.  The initialization logic, however, was expecting to get time in units of days.

localtime:  Default zoneinfo directory is /etc/zoneinfo instead of /usr/local/etc/zoneinfo which results in a longer pathname than the default 32 characer MAX

Allow NSH date command with no RTC.  This command is useful without an RTC too.  Also, this permits testing on the simulator which never has an RTC

Fixes to asinh(), atanh(), and sinh(): The 'basic' expansions all exhibited bad cancellation errors near zero (<= 1E-10). This can be easily seen e.g. with x = 1E-30, the results are all zero though they should be extremely close to x. The cutoff values (1E-5, 1E-9) are chosen so that the next term in the Taylor series is negligible (for double). Functions could maybe be optimized to use only first term (x) and a smaller cutoff, just bigger than where the cancellation occurs.

SAM3/4 and SAMV7 UART:  The IMR register is read-only.  This means that sam_restoreints() does not actually re-enable UART interrupts.