Duplicate declaration warnings if puppet-windows_env is used, too

[heini]

With both this module and puppet-windows_env installed, one gets duplicate declaration warnings for two constants used in the code:

C:/ProgramData/PuppetLabs/puppet/cache/lib/puppet/provider/windows_env/windows_env.rb:51: warning: already initialized constant HWND_BROADCAST
C:/ProgramData/PuppetLabs/puppet/cache/lib/puppet/provider/windows_path/path_provider.rb:9: warning: previous definition of HWND_BROADCAST was here
C:/ProgramData/PuppetLabs/puppet/cache/lib/puppet/provider/windows_env/windows_env.rb:52: warning: already initialized constant WM_SETTINGCHANGE
C:/ProgramData/PuppetLabs/puppet/cache/lib/puppet/provider/windows_path/path_provider.rb:11: warning: previous definition of WM_SETTINGCHANGE was here

PR to come...