After a bug introduced in 6f24148 SpeedUp is now properly working again.

Fixes: #930
Correct Enable/Disable Up/Down button when Min/Max changes
Fix CaretBrush

Resolves #937
Merge pull request #931 from xxMUROxx/hotfix/NUD-SpeedUp-NotWorkingProperly

[HOTFIX] NumericUpDown SpeedUp is now properly working again.