Azure Pipelines configuration (#346)

Add a new CI system for Linux/macOS/Windows, Azure Pipelines
Configuration based on https://github.com/crate-ci/azure-pipelines

Since crate-ci defaults to failing the build on clippy errors, forked to:
https://github.com/iceiix/azure-pipelines/tree/clippy
with configurable clippy parameters, to allow disabling the hard failures
(until the underlying causes for the warnings can be fixed).

* Allow erroring clippy float_cmp and unsafe ptrs

* Relax allowed clippy warnings

* Install xcb libraries for -lxcb-shape, -lxcb-xfixes

azure-pipelines.yml

@@ -0,0 +1,17 @@
+jobs:
+ - template: default.yml@templates
+   parameters:
+     setup:
+       - script: sudo apt-get install libxcb-composite0-dev libx11-dev
+         displayName: "Install build dependencies"
+         condition: eq(variables['Agent.OS'], 'Linux')
+     minrust: 1.44.1
+     clippy: -A clippy::temporary_cstring_as_ptr -A clippy::not_unsafe_ptr_arg_deref -A clippy::float_cmp
+
+resources:
+  repositories:
+    - repository: templates
+      type: github
+      name: iceiix/azure-pipelines
+      ref: c50d2b8335a6b1856aa2fc4f5f41f6684ef8580c
+      endpoint: iceiix