textarea: height and buffer-level max line settings

[meowgorithm]

I'm noticing a few things while working with textarea:

• The maximum number of lines and height cannot exceed 99
• The maximum number of lines in the buffer is determined by the height and max height
• The maximum number of lines in the buffer cannot be less than the height and max height

We should ultimately be able to control the number of lines in the buffer independently from of the height.