Eliminate some warnings in normal_distribution_base.
If no minimum_system can be found, return a tuple of systems rather than issuing a compilation error.
Eliminate use of retag & reinterpret_tag in algorithm implementations.

Fixes #364364364
Avoid unwrapping wrapped references in transform_iterator's
implementation.

Fixes #379
Merge pull request #402 from jaredhoberock/issue-379

Avoid unwrapping wrapped references in transform_iterator's
Merge pull request #403 from jaredhoberock/issue-364

Issue 364