Never consider submodules for stashing

...before the helper's cleanup method tries to delete their files.

Fix x86/x64 size_t related warnings

Remove leading newlines from commit message

Fix libgit2/libgit2sharp#522

Add refdb.h to git2.h, reorder git2.h sanely

Win32: handle http->https redirects

Bring error handling docs up to date

The error handling docs date back to the early error redesign
work and don't match up with the route we actually took.  This
brings them in line with actual practice both for external users
and internal implementors, and notes some of the exceptions and
possible bugs.

That's the refdb, it's not the odb...

Cleaned up some tables in checkout-internals doc

Fixed formatting of diff-internals.md

Indentation for lists was not working correctly.

The markdown wasn't rendering correctly.

Make tests pass if XDG config exists

Alternative fix for cross protocol redirects

The subtransport path was relying on pointing to data owned by
the remote which meant that after a redirect, the updated path
was getting lost for future requests.  This updates the http
transport to strdup the path and maintain its own lifetime.

This also pulls responsibility for parsing the URL back into the
http transport and isolates the functions that parse and free that
connection data so that they can be reused between the initial
parsing and the redirect parsing.

Ignore files that disappear while iterating

On occasion, files can disappear while we're iterating the
filesystem, between calls to readdir and stat.  Let's pretend
those didn't exist in the first place.

Various warning cleanup and minor fixes

Minimize regex usage

The git_buf_text_gather_stats call returns a boolean indicating if
the file looks like binary data.  That shouldn't be an error; it
should be used to skip CRLF processing though.

'del' instead of 'delete' for the poor C++ users

This replaces some git_buf_printf calls with simple calls to
git_buf_put instead.  Also, it fixes a missing va_end inside
the git_buf_vprintf implementation.