Headers: mark arm_acle.h with extern "C"

Although the functions are marked as always_inline, the compiler with which they
are used may not honour the extended attributes and emit them as functions.  In
such a case, indicate that they should have extern "C" linkage and should not be
mangled in C++ style if used within C++.

llvm-svn: 212511

clang/lib/Headers/arm_acle.h

@@ -30,6 +30,10 @@
 
 #include <stdint.h>
 
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
 /* Miscellaneous data-processing intrinsics */
 
 static __inline__ uint32_t __attribute__((always_inline, nodebug))
@@ -140,4 +144,8 @@ static __inline__ uint32_t __attribute__((always_inline, nodebug))
 }
 #endif
 
+#if defined(__cplusplus)
+}
+#endif
+
 #endif /* __ARM_ACLE_H */