Semantic changes to tor_calloc
I noticed the improvements to tor_malloc_zero with tor_calloc, and I added a bit to that.
The tor_calloc function overflow check is a bit faster; the semantic patch changes the argument order to be like calloc; and some other small details.
The branch is "calloc" at: https://bitbucket.org/eliteraspberries/tor/branch/calloc
Everything seems to work fine on the stable release.