Migration to meson

• Use meson as build system
• Removed obsolete Xinerama

Thanks to Charadon

Shell completion

• Added shell completion (bash, zsh)
• Version argument
• Fixes

Daemon mode and fixes

• Added a daemon mode (--daemon)
• Fixed memory leak

Reworked and multi monitor support

• Added multi monitor support with XRandR or Xinerama
• Changed output

Anit-aliasing fixed

• Fixed anti-alias usage:
  • Anti-aliasing is no longer required for non-native resolution GIFs
  • The anti-alias-off option now became anti-alias,
    so the functionality is inverted, too
• Fix: Image information printing was somewhat disordered

Core fixes and features

• Fixed segfault when no global color table is available
• Fixed image disposition
  • Fixed DISPOSE_BACKGROUND
  • Added DISPOSE_PREVIOUS

Important fixes

Bugfixes:

• Performance mode upscales framerate, if below target
• GIF DelayTime handling
• GIF Information