Use ptrace options to follow children.

This is a possible fix to Parrot missing events for multi-threaded processes.
wait for child to start
Use EXITKILL ptrace option to ensure cleanup.

This is just an extra measure on top of what we already do using the watchdog
and signal handling.

Fixes #28.
Only modify fork/clone if necessary.
Continue the tracee after attaching.
Remove wq_reset since there is no visible use-case.
Internally, release_all_workers() can be used to achieve the same function.
Merge master.

Conflicts:
	parrot/src/pfs_main.cc
Add parrot_pack to .gitignore.
Silece unused variable warning.
Use itable to avoid compiler warning.

I don't see an easier way around this warning from gcc 4.9.0:

COMPILE pfs_main.o
pfs_main.cc: In function ‘void handle_event(pid_t, int, rusage*)’:
pfs_main.cc:356:47: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
       set_insert(stopped_threads, (void *) p->pid);
                                               ^
cc1plus: all warnings being treated as errors
../../Makefile.rules:9: recipe for target 'pfs_main.o' failed

Introduced in 97fb3f42713be6a5698b6e4d0ddcc5e700155dd9.
Use ptrace options for tracing children.

Fixes #60, #28.

* ccl/pull/472/head:
  Continue the tracee after attaching.
  Only modify fork/clone if necessary.
  Use EXITKILL ptrace option to ensure cleanup.
  wait for child to start
  Use ptrace options to follow children.
Update CCL URL.
Merge pull request #475 from dpandiar/master

Remove wq_reset since there is no visible use-case.
Update CCL URL.

* ccl/pull/477/head:
  Update CCL URL.
Fix a problem where D_DEBUG == D_SYSCALL.
FIX: logging of 'cvmfs not found'
Fix pointer error in whole_string_match_regex.
Code should look for dollar at end of pattern, not end of text.
FIX: logging of 'cvmfs not found'

* ccl/pull/480/head:
  FIX: logging of 'cvmfs not found'
Fix pointer error in whole_string_match_regex.

* ccl/pull/481/head:
  Fix pointer error in whole_string_match_regex. Code should look for dollar at end of pattern, not end of text.
add spectool (download, combine and repeat experiments)