Add sk_calloc.  Remove SkMemory_stdlib, which seems unused.

I'm seeing basically no difference between malloc + bzero and calloc on my desktop, but on a Galaxy Nexus calloc is never slower, and significantly faster once the allocation size becomes large, both for allocation and for _reading_.

BUG=skia:1662
R=reed@google.com

Review URL: https://codereview.chromium.org/24251008

git-svn-id: http://skia.googlecode.com/svn/trunk/src@11414 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed