ip2unix: 2.1.2 -> 2.1.3

Upstream fixes:

  - Pass linker version script to the linker instead of the compiler.
  - Compile with `-fPIC` again (regression from version 2.1.2).
  - Out of bounds array access in `globpath`.
  - Handling of `epoll_ctl` calls (they're now replayed after replacing
    socket).
  - GCC 10 build errors and Clang warnings.

While most of these fixes are more relevant for other distros, the
linker script fix is actually a regression existing since a long time
(version 1.x) and caused libip2unix to expose way too many symbols.

Built and tested on i686-linux and x86_64-linux.

Signed-off-by: aszlig <aszlig@nix.build>