Fix several ignore and attribute file behavior bugs

Ignore patterns that ended with a trailing '/*' were still needing
to match against another actual '/' character in the full path.
This is not the same behavior as core Git.

Instead, we strip a trailing '/*' off of any patterns that were
matching and just take it to imply the FNM_LEADING_DIR behavior.

There was a latent bug where files that use macro definitions
could be parsed before the macro definitions were loaded.  Because
of attribute file caching, preloading files that are going to be
used doesn't add a significant amount of overhead, so let's always
preload any files that could contain macros before we assemble the
actual vector of files to scan for attributes.

When traversing the directory structure, the iterator pushes and
pops ignore files using a vector.  Some directories don't have
ignore files, so it uses a path comparison to decide when it is
right to actually pop the last ignore file.  This was only
comparing directory suffixes, though, so a subdirectory with the
same name as a parent could result in the parent's .gitignore
being popped off the list ignores too early.  This changes the
logic to compare the entire relative path of the ignore file.

Introduce core.safecrlf handling

The checks to see if files were out of date in the attibute cache
was wrong because the cache-breaker data wasn't getting stored
correctly.  Additionally, when the cache-breaker triggered, the
old file data was being leaked.

In the threading tests, I was still seeing a race condition where
the same item could end up being inserted multiple times into the
index.  Preserving the sorted-ness of the index outside of the
`index_insert` call fixes the issue.

This is a big refactoring of the attribute file cache to be a bit
simpler which in turn makes it easier to enforce a lock around any
updates to the cache so that it can be used in a threaded env.
Tons of changes to the attributes and ignores code.