Remove expired ports:
2019-08-31 devel/pure-stldict: Depends on expiring devel/llvm35
2019-08-31 lang/dmd1: No longer supported upstream
2019-08-31 lang/gprolog: Abandonware upstream (more than five years), fails in various ways with remotely recent compilers
2019-08-31 math/pure-mpfr: Depends on expiring devel/llvm35
2019-08-31 math/pure-rational: Depends on expiring devel/llvm35
2019-08-31 net/pure-sockets: Depends on expiring devel/llvm35
2019-08-31 textproc/pure-csv: Depends on expiring devel/llvm35
2019-08-31 textproc/pure-xml: Depends on expiring devel/llvm35
2019-08-31 x11-toolkits/pure-tk: Depends on expiring devel/llvm35
2019-08-31 databases/pure-sql3: Depends on expiring devel/llvm35
2019-08-31 devel/pure-readline: Depends on expiring devel/llvm35
2019-08-31 devel/pure-stllib: Depends on expiring devel/llvm35