fix unused variable warnings

Fix the error message handling. Thanks to Christos for noticing.

Replace printf() in child process with a simple write(STDERR_FILNO,...)

Thanks, Joerg.

Rather than just sleeping and hoping that all the sub-processes are
ready to be ptrace()d, use a positive barrier.

White-space in for(...) loops.
Use #define instead of static variables to define test parameters.
No functional change.

Create a variable for max number of passes to make. While we're here,
reduce the pass-count from 100 to 50; this is more than enough to prove
that the test is working, and helps reduce the ever-inc

Create a variable for max number of passes to make. While we're here,
reduce the pass-count from 100 to 50; this is more than enough to prove
that the test is working, and helps reduce the ever-increasing time it's
taking to run the entire test suite.

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Wait a little bit after fork()ing the lockers to give them a chance to
get started before trying to ptrace(ATTACH). Otherwise, the traced
process doesn't seem to resume properly upon ptrace(DETACH)

Wait a little bit after fork()ing the lockers to give them a chance to
get started before trying to ptrace(ATTACH). Otherwise, the traced
process doesn't seem to resume properly upon ptrace(DETACH) and on the
next pass the ptrace(ATTACH) just hangs forever, causing the test to
time-out.

XXX The failure-to-resume-properly might actually be a kernel bug that
we need to follow up on. But for now, let's make the test work as
intended.

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Check that we did get EDEADLK error, and fail immediately if we did not.

Add ATF version of the file locking test