Improvements in TimerTest.cpp.

I realized a couple issues after some further reading: (1) apr_sleep() operates on microseconds, not milliseconds, and (2) microsecond accuracy cannot be guaranteed on Windows platforms.  To address (1) I have renamed the variable, and to address (2) I have increased the time from 100 microseconds to 100 milliseconds to ensure this Timer Test functions even if only millisecond accuracy is guaranteed.