Reinstate errors for unused variables and imports.
Remove obsolete FIXME comment.
Call from_base64 on a vector slice rather than a string slice (fixes #2877).
Merge pull request #3329 from Ms2ger/2877-base64

Call from_base64 on a vector slice rather than a string slice (fixes #2877).
Merge pull request #3328 from Ms2ger/fixme-customevent

Remove obsolete FIXME comment.
Merge pull request #3327 from metajack/cargo-profiles

Reinstate errors for unused variables and imports.