When compiling YARA without Python bindings, stdbool.h is actually used
if it can be used. However Python bindings completely ignore it resulting
in YARA defining its own bool type with sizeof(bool) == sizeof(int).
However before [#1377](https://github.com/VirusTotal/yara/pull/1377), this
can result in different compilation units using different sizes of
bool type and chaos ensues.