[Bug sanitizer/59061] Port leaksanitizer

[earthdok at google dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59061

--- Comment #37 from Sergey Matveev <earthdok at google dot com> ---
I've patched LSan to use the real memset(). At least on my machine this brought
no performance improvement compared to kcc's latest change (just FYI - not
trying to make any point).

As of now, LSan will still clear out the entire small chunk (which can be up to
128KB in size), compared to a default of just the first 4KB in ASan. I'm
undecided as to whether this is worth changing.