Add a futures executor and example

Author: tylerwhall

rust/sysroot-stage2/Cargo.lock

@@ -15,6 +15,9 @@ path = "../zephyr-logger"
 [dependencies.zephyr-uart-buffered]
 path = "../zephyr-uart-buffered"
 
+[dependencies.zephyr-futures]
+path = "../zephyr-futures"
+
 [profile.release]
 lto = true
 panic = "abort"

rust/sysroot-stage2/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "zephyr-futures"
+version = "0.1.0"
+authors = ["Tyler Hall <tylerwhall@gmail.com>"]
+edition = "2018"
+
+[dependencies]
+zephyr = { path = "../zephyr" }
+log = "0.4"
+futures-preview = "=0.3.0-alpha.17"
+futures-util-preview = "=0.3.0-alpha.17"