Cleanup foo.h headers and __config to work in C

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@252274 91177308-0d34-0410-b5e6-96231b3b80d8

include/stdlib.h

@@ -94,6 +94,7 @@ void *aligned_alloc(size_t alignment, size_t size);                       // C11
 #include_next <stdlib.h>
 
 #ifdef __cplusplus
+
 extern "C++" {
 
 #ifdef _LIBCPP_MSVCRT
@@ -123,6 +124,7 @@ inline _LIBCPP_INLINE_VISIBILITY lldiv_t div(long long __x, long long __y) _NOEX
 #endif // _LIBCPP_MSVCRT / __sun__ / _AIX
 
 }  // extern "C++"
+
 #endif  // __cplusplus
 
 #endif  // _LIBCPP_STDLIB_H