Allocators

I haven't necessairly vetted all of these, especially the crossed out ones.

Allocator	Repository	Rust Crate(s)
jemalloc	github.com/jemalloc/jemalloc	jemallocator, jemalloc-sys, jemalloc
dlmalloc		dlmalloc (port!)
tcmalloc	github.com/google/tcmalloc	tcmalloc, tcmalloc-sys