Generic C vector that grows the buffer exponentially instead of by a fixed size (or worse, by 1), trading memory efficiency for computational efficiency. This is typically used by libraries such as C++'s STL. Inspired by things like stb_ds.h
I did only very basic testing. By default, the vector is resized to 1.5*size(vec)
when full. You can change the constant by defining GROWTH_EXP