[haxe mode] A not-so-great fix to an indentation bug

Closes #3500

I don't know if

1) there's a way to get haxe to, while in functiondef, for instance,
   be able to tell the compiler that what it thought was a type name
   is actually a variable name, and to indent/highlight correctly

or

2) there's a way that, assuming it's a type name, to still indent
   correctly

but it is possible to loosen the lexer to accept things marked as
types as function names (in functiondef), and this fixes the
indentation problem.