Take into account leap seconds in AUX messages' timestamps

[ifakhrutdinov]

Proposed changes

The PR adds code to get the current amount of leap seconds and subtract that from the STCK value which goes into the timestamps.

Additional changes:

• Pick up the cross-memory changes in zowe-common-c
• Update the changelog with these changes

This PR addresses Issue: #690

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Change in a documentation
• Refactor the code
• Chore, repository cleanup, updates the dependencies.
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

PR Checklist

Please delete options that are not relevant.

• If the changes in this PR are meant for the next release / mainline, this PR targets the "staging" branch.
• My code follows the style guidelines of this project (see: Contributing guideline)
• Relevant update to CHANGELOG.md
• My changes generate no new warnings

Testing

• Start ZIS with AUX;
• Compare the timestamps from the beginning of the JES and SYSPRINT logs; the timestamps should match.

[JoeNemo]

Approved