Log Message:
tmux: Fix build on Solaris due missing paths.h defines

Solaris has paths.h but does not define all _PATH_DEFPATH.
Backport upsrteam commit
 <https://github.com/tmux/tmux/commit/92ecd611f68663dfceb2494e637b3ebe51d3fd86>
to address that.

Fixes PR pkg/55065.

Thanks to Joern Clausen for the patch and PR!