traffic_cop: wait() for children on SIGTERM

rework traffic_cop's signal handling to register a handler for
SIGTERM. In this handler we now send SIGTERM to all children
and then wait() for them.
This should allow us to handle restarts in upstart more gracefully.

Finally, we simplify the handling on Linux by no longer parsing
/proc: It's not necessary. Linux is a POSIX system too.

Conflicts:

	lib/ts/lockfile.cc
cleanup: get rid of ink_killall implementation

After ripping it out from the code, remove it the Linux-specific,
/proc parsing ink_killall implementation.
Handle SIGINT the same way as SIGTERM

also, disable debugging again
TS-1609 Fix build issues with gcc-4.7 related to the Cop changes
TS-1657 Traffic Cop doesn't wait() for its children

  Patch: f29b2c71287ba8e440656969198c22039eb7aff8
         f0aaa22098afcc4960a761c67180c5366bf5a5b2
         6424a9c1c4b0b09c97a005240e1e5a206d2e918f
         02d5a927ff27f4189c9dffe1f175e2ee1210ccf4
test/review: igalic, zwoop, oschaaf
backport: igalic
Fix a FreeBSD build error (invalid conversion from 'void*' to 'char*')