contrib: asdcplib: Apply a patch to fix compilation with latest Clang

The asdcplib code contains a C++ template which refers to member
variables that doesn't exist. Earlier, this hasn't been an issue,
as the C++ template never is instantiated, but current Clang
versions (the upcoming 19.x version) diagnoses such issues already
before the class is instantiated, leading to compilation errors
on the asdcplib code.

This applies https://github.com/cinecert/asdcplib/pull/137 (which
hasn't yet received any attention), fixing
https://github.com/cinecert/asdcplib/issues/136.

(cherry picked from commit c481befc)