Merge branch 'jk/xmalloc'

The code is updated to check the result of memory allocation before it is used in more places, by using xmalloc and/or xcalloc calls. * jk/xmalloc: progress: use xmalloc/xcalloc xdiff: use xmalloc/xrealloc xdiff: use git-compat-util test-prio-queue: use xmalloc