midscroll v1.6

Bug-fix release resolving the pointer-speed reset reported in #1 by @ionburger.

Fixed

• Pointer speed / acceleration no longer reset when midscroll starts. Each mouse is now re-emitted through its own uinput mirror that copies the source mouse's name and vendor/product IDs, so libinput/KDE keep applying that mouse's own per-device settings instead of falling back to defaults. Previously every mouse was funneled through a single anonymous virtual pointer, which is why configured speeds appeared to reset.
• Keyboards are no longer grabbed. Device matching now requires both REL_X and REL_Y, so a keyboard exposing a stray pointer capability through its media keys (e.g. the Razer BlackWidow in the issue logs) is left alone.

Notes

• Middle-drag is still hold-and-drag by design (press the wheel and drag to scroll; a quick click passes through as a normal middle click). An optional click-to-toggle mode may come in a later release.
• Packaging bumped to 1.6 for Fedora (RPM), Debian (deb), and Arch (PKGBUILD).

Full changelog: v1.5...v1.6