signature: make the OS give us the offset for git_signature_now

There is a better and less fragile way to calculate time offsets. Let
the OS take care of dealing with DST and simply take the the offset
between the local time and UTC that it gives us.

Passing SSL_VERIFY_PEER makes OpenSSL shut down the connection if the
certificate is invalid, without giving us a chance to ignore that
error. Pass SSL_VERIFY_NONE and call SSL_get_verify_result if the user
wanted us to check.

When no CNs match, we used to jump to on_error which gave a bogus
error as that's for OpenSSL errors. Jump to cert_fail so we tell the
user that the error came from checking the certificate.

Conflicts:
	include/git2/refs.h

Make git_object_peel a bit smarter

refs: expose git_reference_normalize_name()

revwalk: refuse push of non-commit objects

This expands the types of peeling that `git_object_peel` knows
how to do to include TAG -> BLOB peeling, and makes the errors
slightly more consistent depending on the situation.  It also
adds a new special behavior where peeling to ANY will peel until
the object type changes (e.g. chases TAGs to a non-TAG).

Using this expanded peeling, this replaces peeling code that was
embedded in `git_tag_peel` and `git_reset`.

branch: reduce code duplication

Check the type of the pushed object immediately instead of starting the
walk and failing in between.

It's not really needed with the current code as we have EOS and the
sideband's flush to tell us we're done.

Keep the distinction between processed and received objects.

This poor transport was forgotten in the recent sideband support.

Make sure that idx->pack isn't NULL before trying to free resources
under it.

Revparse: GIT_EAMBIGUOUS

Revparse now returns EAMBIGUOUS if the the spec
doesn't match any refs/tags, and is <4 characters.

Add sideband support

Submodule extensions

new config file locations and defaults

As of git v1.7.12, $HOME/.config/git/ is supported as a new
location for "config", "attributes", and "ignore" files.

Depending on what you had done before adding new items to the
internal ignores list, it was possible for the cache of ignore
data to be uninitialized.

Just clean up valgrind warnings about uninitialized memory
and also clear out errno in some cases where it results in
a false error message being generated at a later point.

This lets us notify the user of what the remote end is doing while we
wait for it to start sending us the packfile.

This is a big redesign of the git_submodule_status API and the
implementation of the redesigned API.  It also fixes a number of
bugs that I found in other parts of the submodule API while
writing the tests for the status part.

This also fixes a couple of bugs in the iterators that had not
been noticed before - one with iterating when there is a gitlink
(i.e. separate-work-dir) and one where I was treating anything
even vaguely submodule-like as a submodule, more aggressively
than core git does.

This fixes up a number of problems flagged by valgrind and also
cleans up the internal `git_submodule` allocation handling
overall with a simpler model.

This replaces the old submodule API with a new extended API that
supports most of the things that can be done with `git submodule`.

We can't always rely on the network telling us when the download is
finished. Recognize it from the indexer itself.

Add git_repository_init_ext for power initters