Count mingw as windows.

Closes gh-230

doc-src/HAML_CHANGELOG.md

@@ -3,6 +3,10 @@
 * Table of contents
 {:toc}
 
+## 3.0.17 (Unreleased)
+
+* Understand that mingw counts as Windows.
+
 ## 3.0.16
 
 [Tagged on GitHub](http://github.com/nex3/haml/commit/3.0.16).

doc-src/SASS_CHANGELOG.md

@@ -5,14 +5,14 @@
 
 ## 3.0.17 (Unreleased)
 
-[Tagged on GitHub](http://github.com/nex3/haml/commit/3.0.17).
-
 * Disallow `#{}` interpolation in `@media` queries or unrecognized directives.
   This was never allowed, but now it explicitly throws an error
   rather than just producing invalid CSS.
 
 * Make `sass --watch` not throw an error when passed a single file or directory.
 
+* Understand that mingw counts as Windows.
+
 ## 3.0.16
 
 [Tagged on GitHub](http://github.com/nex3/haml/commit/3.0.16).

lib/haml/util.rb

@@ -374,7 +374,7 @@ module Haml
     #
     # @return [Boolean]
     def windows?
-      RbConfig::CONFIG['host_os'] =~ /mswin|windows/i
+      RbConfig::CONFIG['host_os'] =~ /mswin|windows|mingw/i
     end
 
     ## Cross-Ruby-Version Compatibility