Subtitles: Add z-cord limit removed in 8f3d30412adad6bfa152c6ebf8738965bb79cf28.

Without limit we transform points not relalistic to render.

Add const to some values and remove definition of values used only once.
Rasterizer: Remove sanity checks.

They are imperfect and can cause valid "sane" subtitles to not
show. Instead check for memory allocation failures.
Properly catch bad allocation exception.