libroot: Accept NULL for the resolved_name argument of realpath()

as specified in IEEE Std 1003.1, 2013 Edition, see
http://pubs.opengroup.org/onlinepubs/9699919799/functions/realpath.html

In this case, the returned buffer is allocated with realpath() and can be
deallocated by the caller with free().
The behavior was only "implementation defined" in previous revisions like
IEEE Std 1003.1, 2004 Edition, see
http://pubs.opengroup.org/onlinepubs/000095399/functions/realpath.html

Signed-off-by: Jérôme Duval <jerome.duval@gmail.com>

Introduce __set_errno() throughout libroot.

* add errno_private.h, which defines the __set_errno() macro with
and without tracing
* instead of setting errno manually, all libroot's code now invokes
__set_errno(), which makes it much easier to trace changes to errno
* redirect glibc's use of __set_errno() to our own version

* Replaced the broken BSD realpath() that is neither thread-safe nor POSIX
compliant with one that is both, and magnitudes faster at that, too.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31498 a95241bf-73f2-0310-859d-f6bbb57e9c96

libroot: Accept NULL for the resolved_name argument of realpath()

as specified in IEEE Std 1003.1, 2013 Edition, see
http://pubs.opengroup.org/onlinepubs/9699919799/functions/realpath.html

In this case, the returned buffer is allocated with realpath() and can be
deallocated by the caller with free().
The behavior was only "implementation defined" in previous revisions like
IEEE Std 1003.1, 2004 Edition, see
http://pubs.opengroup.org/onlinepubs/000095399/functions/realpath.html

Signed-off-by: Jérôme Duval <jerome.duval@gmail.com>

Introduce __set_errno() throughout libroot.

* add errno_private.h, which defines the __set_errno() macro with
and without tracing
* instead of setting errno manually, all libroot's code now invokes
__set_errno(), which makes it much easier to trace changes to errno
* redirect glibc's use of __set_errno() to our own version

* Replaced the broken BSD realpath() that is neither thread-safe nor POSIX
compliant with one that is both, and magnitudes faster at that, too.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31498 a95241bf-73f2-0310-859d-f6bbb57e9c96