Rework 'get_timer_usec()', use a C++11 clock if possible.

dev_interface.cpp, dev_interface.h, os_win32.cpp: Move function ...
utility.cpp, utility.h: ... to here.
configure.ac: Remove related checks.

git-svn-id: https://svn.code.sf.net/p/smartmontools/code/trunk@5219 4ea69e1a-61f1-4043-bf83-b5c94c648137