libsodium 0.3 (new formula)

References #17275.
opencv: requires Xcode

Could probably patch for CLT-only, but I don't have a machine
to test on - @adamv
opam 0.9.5

Closes #18334.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
unac: look for iconv_open

The function that unac's configure script needs to check for seems to
be "iconv_open" now, not "libiconv_open".

Closes #18108.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
ranger 1.6.0

Closes #18337.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
open-scene-graph: use /usr/bin/sw_vers to determine osx version

current behaviour uses SDKSettings.plist to determine osx version but this
file is only available when XCode is installed.

Closes #18210.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>