Drush 6.1.0

Closes #22786.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
gradle 1.8

Closes #22784.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
update: untap/retap formulae before/after pull.

This should fix problems like #19799 where we pull formulae from taps
into core. I want to get something similar merged ASAP so we can pull
GCC into core (see #20678).

Closes #19799.
update: handle realpath exception.