Fixes #511. Use INT64 for SYSTEM_CLOCK

[mathomp4]

Description

Uses INT64 for system_clock() calls in MAPL. This should prevent negative throughputs.

I also changed all the other places I saw system_clock() that could be in libMAPL.a. Note there are some programs and tests that are still INT32 but I figure they don't quite need it.

Related Issue

Closes #511

Motivation and Context

Can prevent rare negative throughputs, and other timers.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Trivial change (affects only documentation or cleanup)

Checklist:

• I have tested this change with a run of GEOSgcm (if non-trivial)
• I have added one of the required labels (0 diff, 0 diff trivial, 0 diff structural, non 0-diff)
• I have updated the CHANGELOG.md accordingly following the style of Keep a Changelog

[mathomp4]

Note: I need to actually build and run this, so keeping this as draft at the moment.

[mathomp4]

Tested with a run of GEOS with GNU Debug. Runs and is zero-diff.