aptitude build-dep fails on virtual packages

`aptitude build-dep' fails on some packages, apparently when one of the build dependencies is a virtual package.

For instance, `aptitude build-dep timidity' fails with the error message:

Unable to satisfy the build-depends: Build-Depends: libncurses-dev
Unable to apply some actions, aborting

Now timidity does have libncurses-dev as a build dependency, but it's a virtual package, which on my system is provided by libncurses5-dev. As it happens this is already installed (version 6.1-1ubuntu1.18.04) but aptitude doesn't see to recognize that.

`apt-get build-dep timidity' works correctly, but it would be nice to be able to use aptitude instead. For instance, I'd like to be able to --add-user-tag when doing build-dep, so that I can easily remove all those packages later.

Another example is `aptitude build-dep gnuplot' which fails on the build-depends liblua5.1-dev (provided by liblua5.1-0-dev).

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: aptitude 0.8.10-6ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-33.36-generic 4.15.18
Uname: Linux 4.15.0-33-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.20.9-0ubuntu7.3
Architecture: amd64
Date: Sat Sep 22 11:21:32 2018
SourcePackage: aptitude
UpgradeStatus: Upgraded to bionic on 2018-05-23 (122 days ago)