qxmoji-0.6

• Persist all settings immediately
• Apply all changes to the settings file immediately, watching it for
  external changes
• Generate static emoji data in "ready to use" format (speeding up
  initial display and restoring history)
• Defer initialization of emoji buttons to keep UI responsive
• Build system: generate dependencies while compiling, avoiding extra
  build steps

Bugfixes:

• Direct output to /dev/null when detaching on startup
• Don't draw a background on emoji buttons unless hovered
• Return a failed exit code on startup errors
• Fix several compiler warnings
• Add necessary feature test macros for POSIX and X/Open SUS APIs,
  fixing the build with e.g. GNU glibc (thanks @jhx0 for starting this)