buffer: use v8::TypedArray::kMaxLength as buffer::kMaxLength

This was added in v8 6.2, looks like a safe replacement for
our own buffer::kMaxLength.

PR-URL: #19738
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/node_buffer.h

@@ -31,8 +31,7 @@ extern bool zero_fill_all_buffers;
 
 namespace Buffer {
 
-static const unsigned int kMaxLength =
-    sizeof(int32_t) == sizeof(intptr_t) ? 0x3fffffff : 0x7fffffff;
+static const unsigned int kMaxLength = v8::TypedArray::kMaxLength;
 
 typedef void (*FreeCallback)(char* data, void* hint);