This commit lowers the priority of the darwin backtrace component
below that of the ''execinfo'' and ''stackprint'' components, which
will cause OS X Leopard to use the ''execinfo'' component. execinfo
utilizes a public API for printing the stacktrace. The ''darwin''
component uses some evil hacks and a not-so supported package from
Apple to print the stack trace.
This commit was SVN r17840.