Allow reallocation of gl buffer

[mario-holubar]

When buffer_update() is called with a size greater than the buffer's original size, reallocate it using glBufferData()

Or is the lack of this intentional to incentivize keeping buffers at a fixed size?

[not-fl3]

It was intentional, but if it is easy to make it works with a bigger buffer sizes - I don't really see why not.
The only question here - could it be done for metal backend? I am OK with changing this behavior, but it should be consistent across backends

[mario-holubar]

Ah yeah that makes sense. I've never used Metal so I don't know if it's possible.