ledger: find Homebrew Python when building --HEAD.

When building --HEAD and --with-python, CMake gets confused by multiple
python installations, e.g. when both Homebrew and system Pythons exist
(see https://github.com/Homebrew/homebrew/issues/10393 for one example).
This patch lifts some hacks from
https://github.com/Homebrew/homebrew/blob/51d054c/Library/Formula/opencv.rb
to point CMake to the Homebrew Python only, if one exists and is
installed.

N.B. brew test ledger seems to be  broken when installed --HEAD for
unrelated reasons.

Closes #27095.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
x265 0.8:

update to 0.8
add test
add 16-bit option

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
x265: add 0.8 bottle.

Closes #27204.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
nginx: update 1.4.6 bottle.
dart 1.2.0 (33014)

Closes #27215.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
binwalk 1.3.0

Closes #26768.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
ghostscript: Bump to 9.10

This requires a second patch (from MacPorts), and a refreshing of
the first patch.  Also, we no longer build against a Hombrewed
little-cms2 because it causes build failure.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
ghostscript: add 9.10 bottle.

Closes #27212.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>