additionally, make sure /opt doesn't sneak in our patch

How many times does this have to be spelt?!

Unfortunately, libtool is yet incapable of doing marking symbols as
hidden (not exported) at compilation time.  So lets do it manually.
According to the GCC documentation, this allow some compile-time
optimizations depending on the platform.
This was already done by Damien earlier (and removed during the
plugin headers cleanup).

The check is disabled on Windows, as the compiler accepts the flag,
but generates lots of warnings during compilation.

This should help Doxygen parse VLC headers, and generally makes headers
easier to read. LibVLC already uses a similar approach.

manually merged and tweaked

includes a couple of tweaks by me and will need further testing and cleaning

- Do not probe paths that do not exist (ENOENT).
- If the OS supports open()ing directories (HAVE_FDOPENDIR), do not
  probe paths that cannot be opened.
- Do not probe files whereby fstat() fails.
- Do not probe non-regular files other than directories and block
  devices (previously, only FIFOs were discarded).
- Look for anchor even if fstat() is not supported.

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

Signed-off-by: Felix Paul Kühne <fkuehne@videolan.org>

See http://forum.videolan.org/viewtopic.php?f=14&t=90169

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>