Adds support for .gitignore files to git_status_foreach() and
git_status_file().  This includes refactoring the gitattributes
code to share logic where possible.  The GIT_STATUS_IGNORED flag
will now be passed in for files that are ignored (provided they
are not already in the index or the head of repo).

It turns out that passing NULL for the second parameter of realpath(3)
is not as portable as one might like.  Notably, Mac OS 10.5 and earlier
does not support it.  So this moves us back to a large buffer to get
the realpath info.

Valgrind fixes in smaller pieces

Trees, indices and repos need to be freed

Missed freeing the entry.

This is the first time this error is throw, so use git__throw instead
of git__rethrow.

Calling git_repository_open immediately after git_repository_init
results in memory leaks.

We get the oid of a reference, free the reference, then
convert the oid to a string. We need to convert the oid
before freeing the memory.

Conflicts:
	tests-clay/clay.h
	tests-clay/clay_main.c

Fix some "attributes" related issues

The value returned by MultiByteToWideChar includes the NULL termination character.

Add missing semicolon

Conflicts:
	tests-clay/clay.h
	tests-clay/clay_main.c

Conflicts:
	tests-clay/clay_main.c

`delete` is a reserved keyword in C++.

This updates to implementation of gitattribute macros to be much more
similar to core git (albeit not 100%) and to handle expansion of
macros within macros, etc.  It also cleans up the refcounting usage
with macros to be much cleaner.

Also, this adds a new vector function `git_vector_insert_sorted()`
which allows you to maintain a sorted list as you go.  In order to
write that function, this changes the function `git__bsearch()` to
take a somewhat different set of parameters, although the core
functionality is still the same.

Currently, diff_index passes the full relative path from the
repository root to the callback. In case of an addition, it passes
the tree entry instead of the index entry.

This change fixes the path used for addition, and it passes only
the basename of the path. This mimics the current behavior of
git_tree_diff.

For the diff-index tests, the diff_more test will run multiple
times. Reset the expect_idx counter after each test in order to
allow this.

The git.git implementation allows this, and there is no reason not
to.

The clay test suite files clay.h and clay_main.c are generated by
the clay python script. Teach CMake about this dependency and
remove the generated files from the repository.

Add support for git attribute macro definitions.  Also, add
support for cache flush API to clear the attribute file content
cache when needed.

Additionally, improved the handling of global and system files,
making common utility functions in fileops and converting config
and attr to both use the common functions.

Adds a bunch more tests and fixed some memory leaks.  Note that
adding macros required me to use refcounted attribute assignment
definitions, which complicated, but probably improved memory usage.

This makes libgit2 compliant with the following scenario

$ git ls-remote file:///d:/temp/dwm%20tinou
732d790b702db4b8985f5104fc44642654f6a6b6        HEAD
732d790b702db4b8985f5104fc44642654f6a6b6        refs/heads/master
732d790b702db4b8985f5104fc44642654f6a6b6        refs/remotes/origin/HEAD
732d790b702db4b8985f5104fc44642654f6a6b6        refs/remotes/origin/master

$ mv "/d/temp/dwm tinou" /d/temp/dwm+tinou

$ git ls-remote file:///d:/temp/dwm%20tinou
fatal: 'd:/temp/dwm tinou' does not appear to be a git repository
fatal: The remote end hung up unexpectedly

$ git ls-remote file:///d:/temp/dwm+tinou
732d790b702db4b8985f5104fc44642654f6a6b6        HEAD
732d790b702db4b8985f5104fc44642654f6a6b6        refs/heads/master
732d790b702db4b8985f5104fc44642654f6a6b6        refs/remotes/origin/HEAD
732d790b702db4b8985f5104fc44642654f6a6b6        refs/remotes/origin/master

Added link to vala bindings

Add Perl to the list of bindings.

Includes relevant Clay test