comms/smstools3: Clean up and modernize port

• Remove unneeded pkg-install/pkg-deinstall scripts, and properly use pkg-message to display uninstall message [1]
• Reorder some statements to silence some portlint warnings
• Properly use shebangfix on more files, replacing some REINPLACE_CMDs
• Remove unneeded REINPLACE_CMDs
• Use RLN in place of LN, to correctly create relative symlinks

Reported by: bapt [1]