Fix for Names truncated at 256 bytes

[pmqs]

Partial fix for #690

Heavy use of malloc/realloc in this, so have tested this for leaks/corruption by hacking sanitizer into the build. There are some leaks around mz_crypt_sha_create and mz_zip_writer_entry_open that were already there, so haven't made it worse.

Can post the sanitizer patch if you like.

[pmqs]

Created #717 to report the leaks and hacked sanitizer build is in https://github.com/pmqs/minizip-ng/tree/sanitizer

[nmoinvaz]

I am second guessing whether or not just to use malloc or not. Because alloca requires headers depending on the platform. And also can cause problem/exeception if there isn't enough stack space. I agree it is unlikely, but who knows. alloca is more efficent if using lots of small files in a zip though.

[pmqs]

Yep, I was in two minds about that myself. In the end I decided to avoid hitting the heap when I could keep it all on the stack with alloca. It will be exceptional use-cases of very long filenames/paths (which this fix is designed to address) that will be the problem.

If you think malloc is likely to have less portability issues, I can redo the change easily enough.

[pmqs]

Changed the alloca to malloc for now.

[nmoinvaz]

I have cleaned up and incorporated these changes.