Previous, 'foo/**' would match 'foo', but it shouldn't have. In this
case, not matching 'foo' is what is documented and also seems consistent
with other recursive globbing implementations (like that in zsh).
This also updates the prefix extractor to pull 'foo/' out of 'foo/**'.
Closes#1756
The top-level listing was just getting a bit too long for my taste. So
put all of the code in one directory and shrink the large top-level mess
to a small top-level mess.
NOTE: This commit only contains renames. The subsequent commit will
actually make ripgrep build again. We do it this way with the naive hope
that this will make it easier for git history to track the renames.
Sigh.
