Avoid using the identifier `bool` to improve support with future C
standards. C23 is about to make `bool` a predefined macro (see N2654).
Since the type `cond_expr_t` is part of the public API it will break
client applications. A quick search of the code in Debian shows only
usages in checkpolicy and setools.
Define a new macro signaling the renaming to simplify support of client
applications for new and older versions of libsepol.
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
