Allow any non-nil value to count as true in bool-vector.

Allow any non-nil value to count as true in bool-vector.

Likewise for xd_signature in dbusbind.c.
This is more consistent with the usual practice in Emacs, which is
that any non-nil value counts as true.
* doc/lispref/sequences.texi (Bool-Vectors): Coalesce discussion of how to
print them.  bool-vector's args need not be t or nil.
* src/alloc.c (Fbool_vector): Don't require args to be t or nil.
* src/dbusbind.c (xd_signature): Likewise, for booleans.
* src/data.c, lisp.h (Qbooleanp):
* src/lisp.h (CHECK_BOOLEAN): Remove.  All uses removed.