This can be useful when scripts want to read the entire frame
and pass it on somewhere else (say, write it to a file or use some
library function on it).
This is what users will want in the majority of cases, and switching
to this makes using this function much easier.
However, this does break backwards compatibility. Luckily to my
knowledge this function is not actually used in any existing published
script (all scripts using get_frame just use getPixelFormatted instead)
so the damage shouldn't be too large. But this is also why I'd rather
rip off the band-aid of breaking backwards compatibility now than later.