Fix typo in items_to_tagstream
hidtool.rb: explain-fix

Small wrapper around diff -y, with a pretty printed version of the
original descriptor and the computed fixed descriptor.
build-plist.rb: Use idiomatic 'data' type
Restore 'HIDDefaultBehavior' key

Accidentally dropped in 8f722f7e1ae7098dde974754a3874e6901bd7492.