These are deprecated and replaced with the diffing code in git2/diff.h

This reverts the changes to the GIT_STATUS constants and adds a
new enumeration to describe the type of change in a git_diff_delta.
I don't love this solution, but it should prevent strange errors
from occurring for now.  Eventually, I would like to unify the
various status constants, but it needs a larger plan and I just
wanted to eliminate this breakage quickly.

This fixes several bugs, updates tests and docs, eliminates the
FILE* assumption in favor of printing callbacks for the diff patch
formatter helpers, and adds a "diff" example function that can
perform a diff from the command line.

This reworks the diff API to separate the steps of producing
a diff descriptions from formatting the diff.  This will allow
us to share diff output code with the various diff creation
scenarios and will allow us to implement rename detection as
an optional pass that can be run on a diff list.

Signed-off-by: schu <schu-github@schulog.org>

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>
Signed-off-by: Vicent Marti <tanoku@gmail.com>

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Author:    Carlos Martín Nieto <carlos@cmartin.tk>
#
# On branch development
# Your branch is ahead of 'origin/development' by 11 commits.
#
# Changes to be committed:
#   (use "git reset HEAD^1 <file>..." to unstage)
#
#	modified:   include/git2/tree.h
#	modified:   src/tree.c
#	modified:   tests-clay/clay_main.c
#	modified:   tests-clay/object/tree/diff.c
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#	0001-remote-Cleanup-the-remotes-code.patch
#	466.patch
#	466.patch.1
#	488.patch
#	Makefile
#	libgit2.0.15.0.dylib
#	libgit2.0.dylib
#	libgit2.dylib
#	libgit2_clay
#	libgit2_test
#	tests-clay/object/tree/