Fix bug in gen_pktline() for deletes of missing remote refs

Inline convention

Add Brian Downing to the hall of fame

License Compliance Audit

The usage of the Android derrived code contains a full notice
which must be provided with the source code as per the terms
given at:
https://android.googlesource.com/platform/bionic/+/android-4.0.3_r1.1/libc/bionic/dirname_r.c

The original BSD glibc code contains the notice as given at
http://opensource.apple.com/source/gcc/gcc-5666.3/libiberty/bsearch.c
and should be given in full along with the code.

* gen_pktline() in smart_protocol.c was skipping refspecs that deleted
  refs that were not advertised by the server.  The new behavior is to
  send a delete command with an old-id of zero, which matches the behavior
  of the official git client.
* Update test_network_push__delete() in reaction to above fix.
* Obviate messy logic that handles missing push_spec rrefs by canonicalizing
  push_spec.  After calculate_work(), loid, roid, and rref, are filled in with
  exactly what is sent to the server

The original libpqueue file were licensed under Apache 2.0 so
therefore should retain their copyrights and header as per the
license terms at http://www.apache.org/licenses/LICENSE-2.0

expose merge metadata cleanup

Allow note overwrite

Segregate in-memory and persisted remotes

Update showindex example

I find the showindex example to be pretty useful on occasion, but
there were are couple of output tweaks I wanted, plus I wanted the
ability to specify a path to an actual index file instead of having
to open the whole repository.  This makes those changes and expands
the example slightly.

Alternative fix for iterator memory leak

Fixed compilation with =>VS2010

Starting with VS2010 MS ships a stdint.h.

Signed-off-by: Sven Strickroth <email@cs-ware.de>

When normalizing a reference name, if there is an error because
the name is invalid, then the memory allocated for storing the
name could be leaked if the caller was not careful and assumed
that the error return code meant that no allocation had occurred.

This fixes that by explicitly deallocating the reference name
buffer if there is an error in normalizing the name.

An earlier change to `git_diff_from_iterators` introduced a
memory leak where the allocated spoolandsort iterator was not
returned to the caller and thus not freed.

One proposal changes all iterator APIs to use git_iterator** so
we can reallocate the iterator at will, but that seems unexpected.
This commit makes it so that an iterator can be changed in place.
The callbacks are isolated in a separate structure and a pointer
to that structure can be reassigned by the spoolandsort extension.

This means that spoolandsort doesn't create a new iterator; it
just allocates a new block of callbacks (along with space for its
own extra data) and swaps that into the iterator.

Additionally, since spoolandsort is only needed to switch the
case sensitivity of an iterator, this simplifies the API to only
take the ignore_case boolean and to be a no-op if the iterator
already matches the requested case sensitivity.

Teach UNC paths to git_path_dirname_r()

Fix libgit2/libgit2sharp#256