i think this is more secure.

	this is protect following files match
		error.txt, php.ini, and tpl files (i added caseles version with "(?i)"
		error.TXT, php.INI files can be protected, etc.
	You can find more information http://www.pcre.org/pcre.txt
	At the end i ignore robots.txt file from file match.
Merge pull request #468 from hkulekci/opencart

.htaccess changes for robots.txt