Update sysutils/capistrano to 2.5.19

Upstream changes:

== 2.5.18 / March 14, 2010

Small fix for rolling back if a shell scripts exits non-zero; enabled a rollback
if git (or other) externals fail during the deploy.
* #151 check return code status of system command to create local copy and
rollback if not 0 (David King)

== 2.5.17 / February 27, 2010

Various small bug fixes.

== 2.5.16 / February 14, 2010

Fixed a small regression in 2.5.15

== 2.5.15 / 14 February 2010

Fixes a feature request not to overwrite roles when using the ROLES
environmental variable.
* #126 - The option to not overwriting the roles which are defined in the task
definition.
* Removed the `upgrade` file as it has been a couple of years since 1.x was in
the wild.
* Slight internal re-factor of the way we calculate the `version`

== 2.5.14 / 18 January 2010

Fixes a low-value bug, thanks to Chris G for the well submitted patch:
#139 - Improves consistency of variable lookup, scm variables with a local_
prefix will be honoured with priority locally (Chris Griego)

== 2.5.13 / 6 January 2010

Small maintenance release:
* #118 - Modified CLI test to not load user or system configuration file (Emily
Price)
* #88 - Re-fixed a problem here, massive apologies to all concerned. (Hangover
from 2.5.12)

== 2.5.12 / 5 January 2010

* Tweak the directory version listing (caused a lot of problems, please upgrade
immediately)

== 2.5.11 / December 2009

* Deprecations and other small changes

(gls)