allocator: Add a basic resource allocation crate

This is based on the crosvm resource allocator from commit 107edb3e.
We only have PIO and MMIO address space to handle, and don't have a GPU
specific path and space.
Also, we support allocating a range at a specified address. This is
mostly useful for PIO, but might be also necessary for MMIO.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

vm-allocator/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "vm-allocator"
+version = "0.1.0"
+authors = ["The Chromium OS Authors"]
+edition = "2018"
+
+[dependencies]
+libc = "*"
+vm-memory = { git = "https://github.com/rust-vmm/vm-memory" }