Tcl syntax hilighting does not handle \" quotation mark escapes (BB-11763)

cf. https://bitbucket.org/wilhelmy/eggdrop-urlmagic/src/30e52d3a0460aed4c77f937bb1949885bc78f8cb/urlmagic.tcl?at=default#cl-231

In Tcl, everything is a string, therefore " has the same meaning everywhere: A literal quotation mark character. In the example above, the single occurrence of a " sequence breaks the syntax hilighting for the entire rest of the file.

Please adjust the Tcl lexer to reflect this in the syntax hilighting.