Fixed various problems with the latest stdbool.h changes, including stdbool.h itself:

- SupportDefs.h only includes stdbool.h if included from C
- stdbool.h for C++ now includes a macro for "bool" as defined by that header
- stdbool.h does nothing if __bool_true_false_are_defined is already defined
- stdbool.h no longer defines a _Bool enum, but defines _Bool as unsigned char, as
  previously done by SupportDefs.h (the previous version changed the size).
- The gensyscalls Jamfile now preprocesses its headers in C++ mode so that "bool"
  stays "bool", and doesn't become _Bool.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@12042 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/posix/stdbool.h

@@ -1,21 +1,28 @@
-#ifndef _STDBOOL_H_
-#define _STDBOOL_H_
-/* 
+/*
  * Copyright 2005, Haiku Inc. All Rights Reserved.
  * Distributed under the terms of the MIT License.
-*/
+ */
+#ifndef _STDBOOL_H_
+#define _STDBOOL_H_
+
+#ifndef __bool_true_false_are_defined
 
 #ifndef __cplusplus
-typedef enum { false = 0, true = 1 } _Bool;
-#define true 1
-#define false 0
+//typedef enum { false = 0, true = 1 } _Bool;
+	// ToDo: this would change the bool size compared to standard BeOS
+typedef unsigned char _Bool;
+#	define bool _Bool
+#	define true 1
+#	define false 0
 #else
-typedef bool _Bool;
-#define true true
-#define false false
+#	define _Bool bool
+#	define bool bool
+#	define true true
+#	define false false
 #endif
-#define bool _Bool
 
 #define __bool_true_false_are_defined 1
 
+#endif	// __bool_true_false_are_defined
+
 #endif	/* _STDBOOL_H_ */