Fix git_status_foreach tests

Don't use '__attribute__ visibility' with gcc unless it's at version 4 or better

version 4 or better.

There were quite a few places were spaces were being used instead of
tabs. Try to catch them all. This should hopefully not break anything.
Except for `git blame`. Oh well.

1. The license header is technically not valid if it doesn't have a
copyright signature.

2. The COPYING file has been updated with the different licenses used in
the project.

3. The full GPLv2 header in each file annoys me.

Provided the tests fail (which they should not) and the callback is invoked too many times, this prevents the tests from segfaulting.

This allows to build both test suites at the same time

...Ops, I broke the old test when porting it to Clay.

 - Should increase performance through usage of a walker
 - No callback invocation for unaltered entries

 - fix retrieval of a file status when working against a newly initialized repository
 - reduce memory pressure
 - prevents a directory from being tested

Document GIT_SUCCESS

Warning fixes

pull request for #387

CMakeLists: no need in split debug/release build

As we no longer expose the transport functions, this is now the only
way to connect to a remote when given an URL instead of a remote name

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Transports shouldn't get used outside of the library, so don't expose
accessor functions.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Sockets on Windows are unsigned, so define a type GIT_SOCKET which is
signed or unsigned depending on the platform.

Thanks to Em for his patience with this.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>