Added MySQL UDF to execute commands on the underlying system:

* sys_eval() to return the standard output
* sys_exec() to return the exit status

It's a patched version of http://mysqludf.org/lib_mysqludf_sys/index.php

extra/mysqludfsys/lib_mysqludf_sys/install.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+echo "Compiling the MySQL UDF"
+make
+
+if test $? -ne 0; then
+	echo "ERROR: You need libmysqlclient development software installed "
+	echo "to be able to compile this UDF, on Debian/Ubuntu just run:"
+	echo "apt-get install libmysqlclient15-dev"
+	exit 1
+else
+	echo "MySQL UDF compiled successfully"
+fi
+
+echo -e "\nPlease provide your MySQL root password and press RETURN: \c"
+read PASSWORD
+
+mysql -u root --password=$PASSWORD mysql < lib_mysqludf_sys.sql
+
+if test $? -ne 0; then
+	echo "ERROR: unable to install the UDF"
+	exit 1
+else
+	echo "MySQL UDF installed successfully"
+fi