time: SCTime additions -- neq, initializer

time: SCTime additions -- neq, initializer

Issue: 5818

This commit adds an initializer for the SCTime_t type and a comparison
macro for "not equal".

Use them as follows:
    SCTime_t my_var = SCTIME_INITIALIZER;
    if (SCTIME_CMP_NEQ(sctime1_val, sctime2_val)) {
    }