build/Jamfile overrides <warnings>

[pdimov]

As mentioned in #219, linking to /boost/serialization//boost_serialization/<warnings>off doesn't propagate <warnings>off to Regex, which breaks when warnings-as-errors is on.

That's because build/Jamfile contains

project : requirements
   # default to all warnings on:
   <warnings>all
   : common-requirements <library>$(boost_dependencies)
   : requirements <library>$(boost_dependencies_private)
   ;

which overrides the inherited <warnings>off with <warnings>all.

The comment says "default to all warnings on", but since it's a requirement, it's not a default and is always applied.

It should be put in default-build instead.

[pdimov]

(or removed altogether - <warnings>all should be used when testing, not when building.)