rather than our own copies

This means that PACKAGE_TARNAME gets set, so the default docdir is
correct.

There are now 104 calls to mkdirhier, down from 1201, when validating.

This one complains sometimes, but there's no good way to improve it.

Tidy up the way that predicates are handled inside types

on Windows, as they are now in-tree

This helps on a hyperthreaded CPU by yielding to the other thread in a
spinlock loop.

The changes I made to the tidier recently introduced a serious
regression: the unfoldings for bindings in a recursive group were
sometimes lost, because we were looking at Id occurrences rather than
Id binders, and the occurrences of recursive Ids do not necessarily
have unfoldings attached.

Also add support for testing the bindistprep tarball, for when we are
validating.

This should catch make going into an infinite loop.

We now do all the hard work in a bindistprep subdirectory, and just move
the result to the root directory. This way we can delete anything in
bindistprep/ without worrying about deleting anything important.

In decodeFloat_Int# we have the C-- code:

    mp_tmp1  = Sp - WDS(1);
    mp_tmp_w = Sp - WDS(2);
    
    /* arguments: F1 = Float# */
    arg = F1;
    
    /* Perform the operation */
    foreign "C" __decodeFloat_Int(mp_tmp1 "ptr", mp_tmp_w "ptr", arg) [];
    
    /* returns: (Int# (mantissa), Int# (exponent)) */
    RET_NN(W_[mp_tmp1], W_[mp_tmp_w]);

Which all looks quite reasonable.  The problem is that RET_NN() might
assign the results to the stack (with an unregisterised back end), and
in this case the arguments to RET_NN() refer to the same stack slots
that will be assigned to.

The code generator should do the right thing here, but it wasn't - it
was assuming that it could assign the results sequentially.  A 1-line
fix to use emitSimultaneously rather than emitStmts (plus comments).

added:

 primop  TraceEventOp "traceEvent#" GenPrimOp
   Addr# -> State# s -> State# s
   { Emits an event via the RTS tracing framework.  The contents
     of the event is the zero-terminated byte string passed as the first
     argument.  The event will be emitted either to the .eventlog file,
     or to stderr, depending on the runtime RTS flags. }

and added the required RTS functionality to support it.  Also a bit of
refactoring in the RTS tracing code.

The docs are no longer built and installed separately.