[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, 343, 344 and 362.
would you mind adding `FUNC_ATTR_NONNULL_ALL` here as @aktau mentioned?