This adds a new verb, gy, which behaves exactly like a normal yank
command except it's dot-repeatable. When using the dot-repeat, it
yank-appends with a newline to the register, so it can be used as an
accumulator.

This time, it's using TextChanged and CursorMoved hooks to determine
what the word was before and after a text change occured. This makes it
much cleaner and doesn't rely on remapping anything.

The strategy is now, what was the word before the text was changed, and
what is it after, and have that be the search/replace.

This is very useful for constraining searches to certain scopes such as
searching for a variable within a function or body of code.

Follows the pattern:

i[nl]d[wei] for next/last diagnostic warning/error/info.