Fix &ft check in QuoteDelim: handle dotted filetypes

From `:h 'filetype'`:

		When a dot appears in the value then this separates two filetype
		names.  Example:
			/* vim: set filetype=c.doxygen : */ ~

I am using `ft=pentadactyl.vim` for my Pentadactyl/Vimperator
configuration files.
Merge pull request #162 from blueyed/handle-dotted-filetype

Fix &ft check in QuoteDelim: handle dotted filetypes