Bazel build rules for asio

Follows a "repos/deps" pattern (in order to help with recursive dependencies). To use:

1. Copy bazel/repos.bzl into your repository at 3rdparty/bazel-rules-asio/repos.bzl and add an empty BUILD (or BUILD.bazel) to 3rdparty/bazel-rules-asio as well.

2. Copy all of the directories from 3rdparty that you don't already have in your repository's 3rdparty directory.

3. Either ... add the following to your WORKSPACE (or WORKSPACE.bazel):

load("//3rdparty/bazel-rules-asio:repos.bzl", asio_repos="repos")
asio_repos()

load("@com_github_3rdparty_bazel_rules_asio//bazel:deps.bzl", asio_deps="deps")
asio_deps()

Or ... to simplify others depending on your repository, add the following to your repos.bzl:

load("//3rdparty/bazel-rules-asio:repos.bzl", asio_repos="repos")

def repos():
    asio_repos()

And the following to your deps.bzl:

load("@com_github_3rdparty_bazel_rules_asio//bazel:deps.bzl", asio_deps="deps")

def deps():
    asio_deps()

4. You can then use @com_github_chriskohlhoff_asio//:asio in your target's deps.

5. Repeat the steps starting at (1) at the desired version of this repository that you want to use:

asio	Copy bazel/repos.bzl from:
1.22.1	e513560