More stringent testing of OSX BSD like behavior. Fix BSD mis-detection

on OSX depending on include order.

include/boost/predef/os/bsd.h

@@ -8,6 +8,13 @@ http://www.boost.org/LICENSE_1_0.txt)
 #ifndef BOOST_PREDEF_OS_BSD_H
 #define BOOST_PREDEF_OS_BSD_H
 
+/* Special case: OSX will define BSD predefs if the sys/param.h
+ * header is included. We can guard against that, but only if we
+ * detect OSX first. Hence we will force include OSX detection
+ * before doing any BSD detection.
+ */
+#include <boost/predef/os/macos.h>
+
 #include <boost/predef/version_number.h>
 #include <boost/predef/make.h>