Merge pull request #2741 from PaulBoersma/master

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Merge pull request #2707 from PaulBoersma/master

for version 6.4.18

Merge pull request #2697 from PaulBoersma/master

for version 6.4.17

Merge pull request #2683 from PaulBoersma/master

for version 6.4.16

Merge pull request #2679 from PaulBoersma/master

for version 6.4.14

Merge pull request #2656 from PaulBoersma/master

for version 6.4.13

Merge pull request #2635 from PaulBoersma/master

refactoring to IntervalTier_moveLeft/RightBoundary

Merge pull request #2631 from PaulBoersma/master

for version 6.4.11

Merge pull request #2627 from PaulBoersma/master

for version 6.4.10

Merge pull request #2625 from PaulBoersma/master

for version 6.4.09