timespec.h, etc.: Eliminate use of 32-bit for time_t
Summary
timespec.h, etc.: Eliminate use of 32-bit for time_t
This code had a uint32_t local variable for seconds from a timespec. This was assigning a time_t to a uint32_t and ultimately returning it. This propgated to rtems_timespec_add_to().
Coverity CID 1512527
Closes #5107 (closed).