add support for galera gmcast.segment

[eRadical]

Description

Changed galera_gmcast_segment to galera_use_gmcast_segment to define if you want or not support for gmcast.segment

Related Issue

See issue #6 .

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)
• Chore (non-breaking change that does not add functionality or fix an issue)

Checklist:

• I have read the CONTRIBUTING document.
• I have run the pre-merge tests locally and they pass.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[eRadical]

This need has reappeared on my radar...

Hope this is ok. @mrlesmithjr thoughts?

[geohost]

I really need this! ❤️