Fixes for text objects (mostly text input)

Text input (Flixel & OpenFL) is now uneditable when its component is disabled
Set text input vscrollNativeWheel to true (prevents HaxeUI from handling mouse wheel scrolling, as the text input handles it already) and vscrollPageStep to 1 (moves one line at a time, consistent with the OpenFL backend)
Prevent Flixel text input variables being set to null where it isn't accepted (alignment, bold and italic variables), causing a refresh when it isn't needed
Vscroll values in _inputData for the Flixel text input are now 0-based, which fixes the scroll bar not starting from the very top (consistent with the OpenFL text input)
Removed the keyboard event listeners for the Flixel text input, as it's no longer needed since the latest release, which lets the events be dispatched to the stage
OpenFL text input now sets _inputData.vscrollMax to a 0-based index, consistent with _inputData.vscrollPos
Enable pixelPerfectRender for text display & input, consistent with the components

Before:

After:

haxeui / haxeui-flixel