Add definition for _Bool in C++ mode

_Bool is not defined when importing Foundation with C++ interop enabled
resulting in the missing type. This patch defines _Bool to bool when
compiling for C++.

Author: etcwilde

CoreFoundation/Base.subproj/CFBase.h

@@ -80,6 +80,11 @@
 #if !defined(__MACTYPES__)
 #if !defined(_OS_OSTYPES_H)
 #if DEPLOYMENT_RUNTIME_SWIFT
+
+#ifdef __cplusplus
+#define _Bool bool
+#endif
+
     typedef _Bool                   Boolean;
 #else
     typedef unsigned char           Boolean;