Enable mcrypt extension in PHP

[cah]

1. Need to configure, compile and install libmcrypt-2.5.8

/user/hsiaoc1/software/libmcrypt-2.5.8

NOTE: "yum install libmcrypt" did NOT install mcrypt.h and the next step won't
work.

2. Configure, compile and install mcrypt extension under PHP-5.6.17

2.1. cd /user/hsiaoc1/software/php-5.6.17/ext/mcrypt
2.2. phpize
2.3. aclocal
2.4. ./configure
2.5. make
2.6. make test
2.7. make install

3. Add "extension=mcrypt.so" to php.ini. Check phpinfo.php to find out the locat
ion of php.ini.

4. Restart Apache