Provide and Encode icuabi in libboost-regex shlibdeps.

Take inspiration from other languages that generate unique Provides and shlibdeps, such that we encode the ICU abi in the boost-regex Provides/shlibdeps. This way boost becomes binNMU safe for libicu ABI transitions.

assigned to @pochu

Also pinging @gcs as the icu maintainer. Hopefully with this change, boost & icu abi transitions become untangled forever.

I am uploading this change in Ubuntu, and transitioning to such deps. Also will test how this will help (or not!) with doing icu and boost abi transitions separately.

merged

Do you plan an upload soon? Any problem might arose in Ubuntu?