Merge branch 'pw/xdiff-alloc'

Add a level of redirection to array allocation API in xdiff part, to make it easier to share with the libgit2 project. * pw/xdiff-alloc: xdiff: introduce XDL_ALLOC_GROW() xdiff: introduce XDL_CALLOC_ARRAY() xdiff: introduce xdl_calloc xdiff: introduce XDL_ALLOC_ARRAY()