Have text:pos(x, y) position right-justified texts properly

[Dev-Roland]

Issue:

Right-aligned objects disappear when the self:pos(x, y) function is used on them.

Steps to Reproduce:

local texts = require('texts')
local text = texts.new('Hello world')
text:pos(100,100)
text:right_justified(true)
text:show() -- now you see me
coroutine.schedule(function()
    text:pos(110, 110) -- now you don't
end, 3)

Expected Behavior

The text would not disappear and the text's top-right corner would be at the x/y position passed into the pos function.

[RubenatorX]

Thank you for documenting the bug, but I rather doubt we'd be willing to change this at this point in v4 because it has the potential to break any addons that have gone around the bug.
How to get around the bug:
When setting position while right justified, subtract windower.ui_x_res from the x position before setting it.