Cherry-pick vio_type_name and safe_vio_type_name functions from 11.2

These are taken from the following two commits by Sergei Golubchik <serg@mariadb.org>:

- 7af733a ("perfschema compilation, test and misc fixes")
- 2ac3121 ("perfschema - various collateral cleanups and small changes")

include/violite.h

@@ -39,7 +39,10 @@ enum enum_vio_type
 {
   VIO_CLOSED, VIO_TYPE_TCPIP, VIO_TYPE_SOCKET, VIO_TYPE_NAMEDPIPE,
   VIO_TYPE_SSL, VIO_TYPE_SHARED_MEMORY
+  /* see also vio_type_names[] */
 };
+#define FIRST_VIO_TYPE VIO_CLOSED
+#define LAST_VIO_TYPE VIO_TYPE_SSL
 
 /**
   VIO I/O events.
@@ -173,6 +176,8 @@ void free_vio_ssl_acceptor_fd(struct st_VioSSLFd *fd);
 
 void vio_end(void);
 
+const char *vio_type_name(enum enum_vio_type vio_type, size_t *len);
+
 #ifdef	__cplusplus
 }
 #endif

sql/sql_acl.cc

@@ -176,6 +176,15 @@ TABLE_FIELD_TYPE mysql_db_table_fields[MYSQL_DB_FIELD_COUNT] = {
 const TABLE_FIELD_DEF
 mysql_db_table_def= {MYSQL_DB_FIELD_COUNT, mysql_db_table_fields, 0, (uint*) 0 };
 
+const char *safe_vio_type_name(Vio *vio)
+{
+  size_t unused;
+#ifdef EMBEDDED_LIBRARY
+  if (!vio) return "Internal";
+#endif
+  return vio_type_name(vio_type(vio), &unused);
+}
+
 static LEX_STRING native_password_plugin_name= {
   C_STRING_WITH_LEN("mysql_native_password")
 };

vio/viosocket.c

@@ -598,6 +598,26 @@ enum enum_vio_type vio_type(Vio* vio)
   return vio->type;
 }
 
+static const LEX_CSTRING vio_type_names[] =
+{
+  { STRING_WITH_LEN("Error") }, // cannot happen
+  { STRING_WITH_LEN("TCP/IP") },
+  { STRING_WITH_LEN("Socket") },
+  { STRING_WITH_LEN("Named Pipe") },
+  { STRING_WITH_LEN("SSL/TLS") },
+  { STRING_WITH_LEN("Shared Memory") }
+};
+
+const char *vio_type_name(enum enum_vio_type vio_type, size_t *len)
+{
+  int index= vio_type >= FIRST_VIO_TYPE && vio_type <= LAST_VIO_TYPE
+             ?  vio_type : 0;
+
+  *len= vio_type_names[index].length;
+  return vio_type_names[index].str;
+}
+
+
 my_socket vio_fd(Vio* vio)
 {
   return mysql_socket_getfd(vio->mysql_socket);