(maint) Make loaded 4x functions debuggable

The 4x functions where not debuggable because the source file
was not given to the Kernel.eval of the loaded source string. This
fixes the two loaders (4x functions, and 3x transforming functions).
Merge branch 'PUP-2755_fixes-from-review'
Merge branch 'master' of https://github.com/puppetlabs/puppet