llvm::dwarf::getDebugNamesBucketCount directly returns the bucket
count, via return statement, but it also returns the hash count
via a parameter. This changes the function to return them both as a
std::pair, in the return statement. It also changes the name of the
function to make it clear it returns both values.

Fix clang-format issue. Avoid unnecessary declaration before
initialization.

Make local variables start with uppercase letter.

Make local variables start with uppercase letter.

Fix case of parameter in comment.