Fix memory leak under Windows

The comment about memory ownership in uuid_t::to_string
was misleading as on most platforms the buffer is a field
of the object;
The string allocated in UuidToString() wasn't properly freed
with RpcStringFree()
Signed-off-by: Taras Shpot <taras.shpot@eleks.com>

AUTHORS

@@ -34,6 +34,7 @@ Piotr Trojanek <piotr.trojanek@gmail.com>
 Sebastian Otaegui <feniix@gmail.com>
 Steven McCoy <steven.mccoy@miru.hk>
 Tamara Kustarova <kustarova.tamara@gmail.com>
+Taras Shpot <taras.shpot@eleks.com>
 Tero Marttila <terom@fixme.fi>
 Terry Wilson <terry@logivox.net>
 Vitaly Mayatskikh <v.mayatskih@gmail.com>

src/uuid.cpp

@@ -41,6 +41,8 @@ zmq::uuid_t::uuid_t ()
 
 zmq::uuid_t::~uuid_t ()
 {
+    if (string_buf)
+        RpcStringFree (&string_buf);
 }
 
 const char *zmq::uuid_t::to_string ()

src/uuid.hpp

@@ -58,7 +58,7 @@ namespace zmq
         enum { uuid_string_len = 36 };
 
         //  Returns a pointer to buffer containing the textual
-        //  representation of the UUID. The caller is reponsible to
+        //  representation of the UUID. The callee is reponsible to
         //  free the allocated memory.
         const char *to_string ();