[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.
So this line should turn into:

    m = xcalloc(1, sizeof(matchitem_t));

right? Will test if this change fixes the issues with upstream's version of patch 7.4.344 disappear.