File Move: Escape existing directory name when looking for open files.

[PhilRunninger]

Description of Changes

Closes #1093

When a directory is renamed, all open buffers are examined to see if they live in that directory. If any such files are open, the user is asked if the files should be renamed/reopened. The problem raised in the issue is caused by said examination. The string does not have its backslashes escaped, which causes a numbered subdirectory, \2 for example, to be treated as a regex back reference, which doesn't exist. The solution is to make sure the backslashes are escaped before doing this examination.

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New Version Info

Author's Instructions

• Derive a new MAJOR.MINOR.PATCH version number. Increment the:
  • MAJOR version when you make incompatible API changes
  • MINOR version when you add functionality in a backwards-compatible manner
  • PATCH version when you make backwards-compatible bug fixes
• Update CHANGELOG.md, following the established pattern.

Collaborator's Instructions

• Review CHANGELOG.md, suggesting a different version number if necessary.
• After merge, tag the merge commit, e.g. git tag -a 3.1.4 -m "v3.1.4" && git push origin --tags