ereg* is deprecated in PHP 5.3

Attached a patch with ereg -> preg replacements. Please review

The only ereg* functions left now are in third party libraries.

There is a problem in calculated/questiontype.php
Warning: preg_match() [function.preg-match]: Unknown modifier '<' in C:\moodle\moodle\site\moodle_head\question\type\calculated\questiontype.php on line 1899

This 1899 line explore the math formula.
$safeoperatorchar = '-+/%>:^~<?=&|!'; / */
$operatorornumber = "[$safeoperatorchar.0-9eE]";

while (preg_match("_{(^|[$safeoperatorchar,(])([a-z0-9_]*)\\(($operatorornumber+(,$operatorornumber+((,$operatorornumber+)+)?)?)?
)}",
$formula, $regs)) {

Spotted a couple of stray ereg calls - committed.