Change prescaler dynamically to support bigger periods on 16 bits timers

SAMV7:  Add some conditional logic to handle the case where the board has no 32.768KHz crystal installed

include/nuttx/net/netdev.h and several Ethernet drivers in arch/:  Most network drivers to not support statistics.  Those that do only support them when DEBUG is enabled.  Each driver collects an architecture specific set of statistics and there is no mechanism in place to view those statistics.  Thus, the driver feature was mostly useless.  This change standardizes the driver statistics and puts the definition in the common network device structure defined in netdev.h where they can be accessed by network applications.  All Ethernet drivers that collect statistics have been adapted to use these common statistics.

Fix some conditional compilation.  CONFIG_LIBC_LOCALTIME should be checked in most of the same places wehre CONFIG_TIME_EXTENDED is checked

arch/sim/src: Add a special file system for use with simulator that supports access to the host file system from the simulation.  From Ken Petit

Small bug fix for stm32 lower half timer driver

Added implementation to get 96-bit stm32 unique id

Added a lower-half timer driver for stm32 which is compatible with the upper-half driver located at /drivers/timers/timer.c

Added a lower-half timer driver for stm32 which is compatible with the upper-half driver located at /drivers/timers/timer.c

arch/arm/src/samv7: Add pin configuratinos for SAME70.  Not all verified.  I assume that the SAME70 pin mapping is identical to the SAMV71 minus MediaLB pins