(PUP-2842) Limit platforms on which we install ruby-prof

The ruby-prof gem is not applicable on all platforms.  This
commit simply adds a :platform restriction to the Gemfile.
(PUP-2843) Fix INVALID_HANDLE_VALUE on Windows x64

 - Previous definition in Puppet::Util::Windows::File would work on x86
   but not x64.  Adjust the constant, and share the constant with
   Puppet::Util::Windows::Security.
Merge pull request #2808 from cprice404/bug/master/PUP-2842-limit-platforms-for-ruby-prof

(PUP-2842) Limit platforms on which we install ruby-prof
(maint) Set Travis CI to run two spec runner processes.

Setting Travis CI to use two concurrent processes for running specs.
This should hopefully speed up running specs for pull request CI.
Merge pull request #2812 from peterhuene/maint/travis

(maint) Set Travis CI to run two spec runner processes.
Merge pull request #2809 from Iristyle/ticket/master/PUP-2843-Verify-Win32-constants

(PUP-2843) Fix constants on Windows x64