Log Message:
ykpers: update to 1.20.0

* Version 1.20.0 (released 2019-07-03)
** Add yk_open_key_vid_pid() allowing vid and pid to be specified.
** Documentation fixes.
** Clear potentially sensitive material from buffers.
** Fix potential buffer overwrite.

* Version 1.19.3 (released 2019-02-22)
** Fix capability read.

* Version 1.19.2 (released 2019-02-19)
** Fix test on mac.
** Fix serial read and challenge response.

* Version 1.19.1 (released 2019-02-19)
** Error out on json output with randomSeed.
** Validate more length fields.
** Use correct FormatMessage function on windows.
** Overflow, bounds and error condition checks.
** Try to zero sensitive memory better.

* Version 1.19.0 (released 2018-04-24)
** Add yk_write_device_info().
** Add ykpersonalize cli switch -D for device info.
** Add code for handling personalization interface of major version 5.

* Version 1.18.1 (released 2018-01-16)
** Support reading accesscode and private ID from stdin.
** Parse optional arguments correctly.
** Documentation fixes.
** Fix for ykinfo modhex serial output when it ends with c.
** Treat all firmware versions as supported.

* Version 1.18.0 (released 2017-01-27)
** Let ykchalresp read challenge from a file.
** Add support of working with a numbered key when many connected
Thanks to Thomas Habets <habets@google.com>
** Documentation clarifications.
** Fixup argument parsing of flags with optional arguments on BSD platforms.
** Fix a file descriptor leak on windows.

* Version 1.17.3 (released 2015-12-28)
** Dont read to much if we don't find a key.
** Text updates to make options clearer.
** Correct logic for question when mode switching to non-otp mode.
** Add 4.3 as supported firmware.

* Version 1.17.2 (released 2015-09-22)
** Let _yk_write() return an error if yk_wait_for_key_status() fails.
** Fix a mistake in help, fixed is up to 16 bytes, 32 characters.
** Add 4.2 as supported firmware.

* Version 1.17.1 (released 2015-04-01)
** Fixup of 1.17.0

* Version 1.17.0 (released 2015-04-01)
** add yk_get_capabilities() to fetch capabilities.
** add -c to ykinfo to fetch capabilities.
** whitelist firmware 4.1.x

* Version 1.16.4 (released 2015-03-23)
** change the tool to accept autoeject time as a short instead of a byte

* Version 1.16.3 (released 2015-03-10)
** whitelist YubiKey version 3.4.x
** only try to set libusb configuration if it's unset on the device

* Version 1.16.2 (released 2014-11-28)
** ykinfo: fix modhex printout when serial is an odd number of hex digits.
** whitelist yubikey version 4.0.x
** try to open more PIDs and add for udev.