Revert "sam_tc_clockselect() reworked to calculate frequency error using smallest possible divisor minimizing the frequency error rather than largest possible divisor which maximized the error."

This reverts commit 5d5851a5.

sam_tc_clockselect() reworked to calculate frequency error using smallest possible divisor minimizing the frequency error rather than largest possible divisor which maximized the error.

Add tools/sethost.sh.   This is a script that you can use to quickly change the host platform from Linux to Windows/Cygwin.  Might save you a lot of headaches.

Add support for the NXP Freedom-K64F board.  This is primarily the work of Jordan Macintyre.  I leveraged this code from https://github.com/jmacintyre/nuttx-k64f

*  This driver supports the 'I2C lcd backpack' design that is based on the PCF8574 io expander.  There's a myriad of different vendors of such, but they are principally the same, save wiring and minor features like jumpers for I2C addresses.  This driver supports known and unknown variants.
*  The interface board supports HD44780-based LCD modules up to 4x32, and this driver accommodates all those formats.

configs/nucleus2g:  Remove this board from the configs/ directory.  A snapshot is still available in the Obsoleted repository

Signals:  Correct implementation of sigset().  It is not just signal() with a different name; it has some additional signal mask handling functionality