New ensure value 'noinclude' for apache::include_file.

This adds support to the apache::include_file definition for putting
a config file in place in the conf.d directory, but without adding an
Include directive in httpd.conf (it will in fact remove any Include
directive referencing the file from httpd.conf).  This is done by
specifying "ensure => 'noinclude'" to apache::include_file.

This is useful if you want to create a configuration fragment that is
supposed to be Include:d from within e.g. a <VirtualHost> section.  An
example is the NSC munin module which wants to do exactly that.