(maint) Update PMT to work around cross-platform issues in Dir.[]

The (unspecified) default behavior of the Dir.[] method, which will implicitly coerce non-String arguments into Strings.  The win32-dir gem
overrides this method and calls String specific methods on the arguments
before any conversions are done.  This change makes our use of the
method in question more explicit, passing Strings instead of Pathname
objects to avoid the interpreter's ire.
(maint) Adding the Usertrust Network CA certificate.

Recent changes have updated the acceptance testing Forge host, which
uses an unknown (to Windows) CA.  This change adds the missing
certificate so that the acceptance tests will pass under Windows.
(maint) Remove FS redefined constant warnings in spec runs

We define FS as an alias for Puppet::FileSystem in three separate
specs. Unfortunately, describe blocks do not provide any namespacing in
rspec, and this were colliding, issuing two separate warnings for a
redefined constant.  Wrapping each spec in its own module provides
separation and elliminates the warnings.
Merge branch 'pr/2584'

* pr/2584:
  (maint) Adding the Usertrust Network CA certificate.

Closes GH-2584
(maint) Adding the Usertrust Network CA certificate.

Recent changes have updated the acceptance testing Forge host, which
uses an unknown (to Windows) CA.  This change adds the missing
certificate so that the acceptance tests will pass under Windows.
Merge pull request #2585 from pvande/maint/master/work_around_platform_inconsistencies_in_Dir

(maint) Update PMT to work around cross-platform issues in Dir.[]
Merge remote-tracking branch 'upstream/stable'

* upstream/stable:
  (maint) Adding the Usertrust Network CA certificate.
Merge remote-tracking branch 'upstream/pr/2586'

* upstream/pr/2586:
  (maint) Remove FS redefined constant warnings in spec runs
Merge branch 'master' of https://github.com/puppetlabs/puppet