src: fix whitespace/blank_line cpplint warnings

PR-URL: https://github.com/nodejs/node/pull/7462
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

src/node_crypto.h

@@ -577,7 +577,6 @@ class SignBase : public BaseObject {
 
 class Sign : public SignBase {
  public:
-
   static void Initialize(Environment* env, v8::Local<v8::Object> target);
 
   Error SignInit(const char* sign_type);

src/node_watchdog.h

@@ -64,6 +64,7 @@ class SigintWatchdogHelper {
 
     int Start();
     bool Stop();
+
   private:
     SigintWatchdogHelper();
     ~SigintWatchdogHelper();

src/node_zlib.cc

@@ -52,7 +52,6 @@ void InitZlib(v8::Local<v8::Object> target);
  */
 class ZCtx : public AsyncWrap {
  public:
-
   ZCtx(Environment* env, Local<Object> wrap, node_zlib_mode mode)
       : AsyncWrap(env, wrap, AsyncWrap::PROVIDER_ZLIB),
         chunk_size_(0),

src/util.h

@@ -286,6 +286,7 @@ class MaybeStackBuffer {
       if (buf_ != buf_st_)
         free(buf_);
     }
+
   private:
     size_t length_;
     T* buf_;