Make installer error out if php was compiled without ctype support.

Make installer error out if php was compiled without ctype support.

This is probably very few people, because you have to actively disable ctype support in order for it not to be compilied in to php. However, there was thread in support desk recently about this ( http://www.mediawiki.org/wiki/Thread:Project:Support_desk/Blank_page_after_install )

(I suppose we could implement work around functions in the case ctype was missing, but doesn't really seem worth it given that its enabled by default, so almost no one will be missing it)