deps: fix RC4 asm in opensslconf.h of 64bit MacOS

The current openssl relase does not use RC4 asm since it explicitly
specified as `$asm=~s/rc4\-[^:]+//;` in
https://github.com/openssl/openssl/blob/OpenSSL_1_0_1-stable/Configure#L584

But iojs has used RC4 asm on MacOS for long time. Fix type of RC4_INT
into `unsinged int` in opensslconf.h of darwin64-x86_64-cc to work on
the RC4 asm.

deps/openssl/config/archs/darwin64-x86_64-cc/opensslconf.h

@@ -129,7 +129,7 @@ extern "C" {
  * - Intel P6 because partial register stalls are very expensive;
  * - elder Alpha because it lacks byte load/store instructions;
  */
-#define RC4_INT unsigned char
+#define RC4_INT unsigned int
 #endif
 #if !defined(RC4_CHUNK)
 /*