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.

The attempt to "clean up warnings" seems to have introduced some
new warnings on compliant compilers.  This fixes those in a way
that I suspect will also be okay for the non-compliant compilers.

Also this fixes what appears to be an extra semicolon in the
repo initialization template dir handling (and as part of that
fix, handles the case where an error occurs correctly).

In revwalk, we are doing a very simple check to see if a string
contains wildcard characters, so a full regular expression match
is not needed.

In remote listing, now that we have git_config_foreach_match with
full regular expression matching, we can take advantage of that
and eliminate the regex here, replacing it with much simpler string
manipulation.

Fix typo in documentation

Make it pair up with the one for commits. This fixes #1691.

Fix warning

OSX 10.8 + Valgrind