os: add version info for kernel and glibc [Linux]

Library/Homebrew/os/linux/glibc.rb

@@ -11,6 +11,14 @@ module OS
 
         @system_version = Version.new version
       end
+
+      def minimum_version
+        Version.new "2.12"
+      end
+
+      def below_minimum_version?
+        system_version < minimum_version
+      end
     end
   end
 end

Library/Homebrew/os/linux/kernel.rb

@@ -0,0 +1,24 @@
+module OS
+  module Linux
+    module Kernel
+      module_function
+
+      def version
+        return @version if @version
+
+        version = Utils.popen_read("uname", "-r").chomp
+        return Version::NULL unless version
+
+        @version = Version.new version
+      end
+
+      def minimum_version
+        Version.new "2.6.32"
+      end
+
+      def below_minimum_version?
+        version < minimum_version
+      end
+    end
+  end
+end