[RFC] Add matchaddpos()-related vim patches. [vim-patch: 7.4.330, 7.4.334, 7.4.343, 7.4.344, 7.4.362]

Adds patches 7.4.330, 334, 344 and 362.
And here, `///<` to document the variable in-line.

Tabs cause formatting errors like this. I don't know why so much of vim has been formatted this way.