respecting nodiscard for fscanf

[kunaltyagi]

Skip early if return value of fscanf is 0 (or negative, though not possible)

This also prevents compiler warnings about discarding the return value of fscanf

[SergioRAgostinho]

This was changed very recently in #3095. clang-tidy flagged them as dead stores. This means we need to manually flag them so that clang-tidy can ignore them safely. See
https://clang.llvm.org/extra/clang-tidy/#suppressing-undesired-diagnostics

[kunaltyagi]

I can't find the clang-tidy config. I assume that's out-of-repo and is set as reported in the commit. I'll take a look and report back

Update

$ clang-tidy -header-filter=.* -checks=-*,clang-analyzer-deadcode.DeadStores -p=build -clang-tidy-binary <path_to_binary_coz _not_in_my_path> ./ml/src/svm.cpp

Says dead-store for 5 fscanf, lines 3261, 3264,3267, 3270, 3273.

As per this FAQ, (void)res is a solution.

Added that to the next commit. Tested with the above command to get 0 warnings