#13 oggvideotools fails to build on gcc-12: ambiguous std::string() constructor

[Sergei Trofimovich]

Upcoming gcc-12 fails build as:

oggvideotools-code/src/main/cmdlineextractor.cpp:270:25: error: call of overloaded 'basic_string(int)' is ambiguous
  270 |   std::string retValue(0);
      |                         ^

Attaching trivial patch.