Remove expired ports:

devel/buildtool-doc
2021-04-01 devel/buildtool: Unmaintained and dead upstream, does not build with -fno-common (llvm 11)
2021-04-01 misc/floatator: Unmaintained and dead upstream, does not build with -fno-common (llvm 11)
2021-04-01 finance/wmstock: Unmaintained and dead upstream, does not build with -fno-common (llvm 11)
2021-04-01 ftp/frox: Unmaintained and dead upstream, does not build with -fno-common (llvm 11)