sed -r is a GNU extension, apparently, and due to stars aligning, this didn't break the build, but led to a totally bogus soname on non-GNU systems. Argh.

Apparently most systems (including GNU, undocumentedly) support -E instead, but perhaps the safest thing is to use a basic regular expression. Unfortunately on many systems ? and + are not available in basic regexes, but using * instead happens to work in our case.

Thanks to @neverpanic for catching this.

Fixes #210