Fix invalid conversion

[davidgatti]

Added this cast since without it the compiler for Particle.io will throw the following error: invalid conversion from 'void_' to 'volatile unsigned char_'. I hope this helps :)

[jcowgill]

void * to volatile unsigned char * is a perfectly acceptable conversion in C. Are you using a C++ compiler instead?

[davidgatti]

http://particle.io does. I'm not compiling this code locally. The code is compiled remotely on their servers.

[simonbutcher]

Hi,

I understand from @pjbakker that we used to compile cleanly using C++ compilers, but this doesn't appear to be the case at the moment. I've raised an issue #477 to track the issue and we'll look into it in case there are any other problems in other configurations.

Thanks for the pull request. I appreciate the fix is trivial, but unfortunately, to accept the contribution and any future contribution we will need a Contributor’s Licence Agreement (CLA) signed by yourself or by whoever has the authority to do so. You can find an agreement to sign here, which can be signed and returned to us, or you could create an mbed account and accept a slightly different agreement here with a click through if this is a personal contribution, which should be simple and quick.

Thanks in advance for your understanding.

[simonbutcher]

Hi,

I tried compiling mbed TLS with g++, and found there were numerous errors in different zeroize functions, so rather than merge the pull request, I fixed them all in one go in commit 88ffc08.

This pull request can now be closed, although there are still too many errors to be able to close #477.

Thanks again for the support of the project!