win: return product name in uv_os_uname() version

Currently, on Windows the uv_utsname_t's version field can
be an empty string if no service packs are installed. This isn't
very helpful, and a lot more information is available in the
Windows registry. This commit prepends the full product name
to the existing service pack information.

Refs: nodejs/node#25843
Refs: libuv#2128 (comment)

src/win/util.c

@@ -1634,6 +1634,10 @@ int uv_os_uname(uv_utsname_t* buffer) {
      https://github.com/gagern/gnulib/blob/master/lib/uname.c */
   OSVERSIONINFOW os_info;
   SYSTEM_INFO system_info;
+  HKEY registry_key;
+  WCHAR product_name_w[256];
+  DWORD product_name_w_size;
+  int version_size;
   int processor_level;
   int r;
 
@@ -1658,18 +1662,58 @@ int uv_os_uname(uv_utsname_t* buffer) {
   }
 
   /* Populate the version field. */
-  if (WideCharToMultiByte(CP_UTF8,
-                          0,
-                          os_info.szCSDVersion,
-                          -1,
-                          buffer->version,
-                          sizeof(buffer->version),
-                          NULL,
-                          NULL) == 0) {
+  r = RegOpenKeyExW(HKEY_LOCAL_MACHINE,
+                    L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",
+                    0,
+                    KEY_QUERY_VALUE,
+                    &registry_key);
+  if (r != ERROR_SUCCESS) {
+    r = uv_translate_sys_error(r);
+    goto error;
+  }
+
+  product_name_w_size = sizeof(product_name_w);
+  r = RegQueryValueExW(registry_key,
+                       L"ProductName",
+                       NULL,
+                       NULL,
+                       (BYTE*) &product_name_w,
+                       &product_name_w_size);
+  RegCloseKey(registry_key);
+  if (r != ERROR_SUCCESS) {
+    r = uv_translate_sys_error(r);
+    goto error;
+  }
+
+  version_size = WideCharToMultiByte(CP_UTF8,
+                                     0,
+                                     product_name_w,
+                                     -1,
+                                     buffer->version,
+                                     sizeof(buffer->version),
+                                     NULL,
+                                     NULL);
+  if (version_size == 0) {
     r = uv_translate_sys_error(GetLastError());
     goto error;
   }
 
+  /* Append service pack information to the version if present. */
+  if (os_info.szCSDVersion[0] != L'\0') {
+    buffer->version[version_size - 1] = ' ';
+    if (WideCharToMultiByte(CP_UTF8,
+                            0,
+                            os_info.szCSDVersion,
+                            -1,
+                            buffer->version + version_size,
+                            sizeof(buffer->version) - version_size,
+                            NULL,
+                            NULL) == 0) {
+      r = uv_translate_sys_error(GetLastError());
+      goto error;
+    }
+  }
+
   /* Populate the sysname field. */
 #ifdef __MINGW32__
   r = snprintf(buffer->sysname,