src: remove unused BITS_PER_LONG macro

Remove the unused and broken BITS_PER_LONG macro.  Broken because x64
is the only 64 bits architecture where it produces the right result.

PR-URL: https://github.com/nodejs/node/pull/4290
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/node_internals.h

@@ -109,12 +109,6 @@ inline static int snprintf(char *buffer, size_t n, const char *format, ...) {
 #endif
 #endif
 
-#if defined(__x86_64__)
-# define BITS_PER_LONG 64
-#else
-# define BITS_PER_LONG 32
-#endif
-
 #ifndef ARRAY_SIZE
 # define ARRAY_SIZE(a) (sizeof((a)) / sizeof((a)[0]))
 #endif