1.0->1.1

    Use "/proc/regs" instead of pstack to get register info. This
    allows us to avoid calls to ptrace() altogether (with the new
    "-n" flag), to avoid interfering with the target process at
    all, with the caveat that a change in the stack while reading
    it may cause pstack to crash.

    Attempt to waitpid with the WLINUXCLONE flag if the first wait
    fails: this allows pstack to suspend linux pthread processes
    correctly. (see PR 39201)

    Fix problem when stack addresses point into the first page of
    memory, confusing the cache into thinking it had already read
    that data.

1.1->1.2
    Cope with changes in 4.7-STABLE threads library: There's no
    longer a context "type" for a thread: all contexts come from a
    jump buffer. The code was not handling the lack of this type
    particulary gracefully, and would spin on a 4.7-STABLE box.

    Don't try to ignore the current thread in the uthread list.
    The conceptual backtrace of the current thread can be different
    to what the actual executing code is. (ie, the thread scheduler
    can be executing as the "current thread", but with a different
    stack to the application's concept of thread)

    Include BP as well as IP in stack traceback when in verbose
    mode.

    "-v" implies "-o" (or -O if -o is already in effect)

    Use "unique id" field in thread for thread-ids. More
    user-friendly than pthread_t pointers.