SERVER-13429 Use logging system in mongod signal handlers, test exit logging.

Still not really safe for signal handlers, but no worse than before,
and correctly logs to the log file/syslog, so an improvement.

(cherry picked from commit f4e6aa9ee7c0dccbb4789d3dff1d92b086d67b88)
SERVER-13429 Eliminate rawOut and related functions

(cherry picked from commit 4e1eccfe64f424daead6ed22542377d2e1ce798e)
SERVER-13429 Remove printStackAndExit

All of the functions in signal_handlers.cpp were broken when logfiles or
syslog were in use. This commit removes them and all callers. The files were
left in place for a later commit to fill them back in with a unified signal
handling system.

(cherry picked from commit 11e43325fa2b0139df1eb9c367b984a5b112dbb4)
SERVER-13429 unify signal handling between mongos and mongod

(cherry picked from commit ad91eb0f75f39c1bb71b5e0ca4279b883cb9fe8d)