Avoid calls to realloc for nvptx

[FX]

Hi Bernd,

I’m afraid I don’t understand the reasoning here:

> Since malloc and free are magically provided by the ptx environment, but realloc is missing, it's nontrivial to provide an implementation for it. The Fortran frontend likes to generate calls to realloc, but in one case it seems like we can compute the old size, and call a function that does malloc/memcpy/free instead.

Does "nontrivial to provide” mean that you don’t provide a realloc() implementation in libc or libgcc? If so, I’m afraid the Fortran compiler will be terminally broken, and fixing just one of the use cases is not sufficient.

FX