ver bump

bump to 1.6.4

Merge pull request #169 from gsmecher/negative_values_rebased

Add support for negative values

Merge pull request #170 from hartwork/fix-linux-ci

Linux CI: Fix Clang 18 + drop Clang 17

Merge pull request #156 from tenox7/dependabot/github_actions/actions…

…/upload-artifact-4.0.0

Actions(deps): Bump actions/upload-artifact from 3.1.3 to 4.0.0

Merge pull request #155 from tenox7/development

Release ttyplot 1.6.0 (fixes #134)

reduce nesting, return early on error

Merge pull request #92 from edgar-bonet/torture-warn

Fix “unused parameter” warning in torture.c

Merge pull request #82 from hartwork/pin-github-actions-at-commit-level

Pin GitHub Actions to specific commits for security

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