resolve template scoping for operator<< past gcc-12 Since gcc-12, and also recent clang versions[1], the template scoping is more picky about having proper declaration of the necessary methods before their definition. The fact that some of the templates have to be resolved in the librostlab aux_functions.h header makes the result a bit confusing, so may be more of a workaround than a real fix. This patch fixes failure to build from source with gcc-12. . [1]: https://clang.llvm.org/compatibility.html#dep_lookup
