Improved Thread Safety of System Time Calls

A review of localtime() behavior has determined this call was not thread safe on all operating systems. Use of this function, and related functions, has been modified. In the case of localtime(), localtime_r() is now used, and similarly with other functions included from the system time libraries.

Note: This system call was also included in the default SQL Types SDK custom callback libraries found in the ctsqlcbk.c module utilized by some customers. This module has been modified as well when available in our code repositories.