Fix off-by-one error in function argument typeinfos
Fix off-by-one error in function argument typeinfos

When gathering type information for function parameters, an invalid index was
being used to store the resulting ErisTypeInfo in the ErisFunction struct.
Also, the actual statement to save the ErisTypeInfo was missing and it gets
added by this patch.

aperezdc/eris,aperezdc/eris,aperezdc/lua-eol,aperezdc/lua-eol