Prefer the faster localhost DB connection, when appropriate.

If the user specifies a DBHostName of 127.0.0.1, but is using standard
MySQL port (3306), use a localhost connection, which will use a Unix
socket connection on *nix or shared memory connection on Windows.

If any user was relying on our previous assumption that specifying a
non-zero DBPort implied you wanted to use a TCP/IP connection, they may
need to specify an appropriate grant allowing access to MySQL via
localhost for the mythtv database user.  If, for some strange reason, a
user wants to use the slower TCP/IP connection to a local MySQL server,
they will need to specify a routable IP address for DBHostName in their
mysql.txt/config.xml.

This should fix the issue Robert K found after 859ad36, and prevent us
from using a slow TCP/IP connection when there's no good reason.

Author: sphery

mythtv/libs/libmythbase/mythdbcon.cpp

@@ -123,8 +123,13 @@ bool MSqlDatabase::OpenDatabase(bool skipdb)
         if (m_dbparms.dbPort)
             m_db.setPort(m_dbparms.dbPort);
 
-        if (m_dbparms.dbPort && m_dbparms.dbHostName == "localhost")
-            m_db.setHostName("127.0.0.1");
+        // Prefer using the faster localhost connection if using standard
+        // ports, even if the user specified a DBHostName of 127.0.0.1.  This
+        // will cause MySQL to use a Unix socket (on *nix) or shared memory (on
+        // Windows) connection.
+        if ((m_dbparms.dbPort == 0 || m_dbparms.dbPort == 3306) &&
+            m_dbparms.dbHostName == "127.0.0.1")
+            m_db.setHostName("localhost");
 
         connected = m_db.open();