vim-patch:7.4.187

Problem:    Delete that crosses line break splits multi-byte character.
Solution:   Advance a character instead of a byte. (Cade Foster)

https://code.google.com/p/vim/source/detail?r=a1c07956171a133583df42627d3498f935e59988
Replace `alloc_check` by `xmalloc`

`alloc_check` is just a wrapper around xmalloc, so we can remove it and use
xmalloc directly. ref #487 / #488

The call was replaced in the following files:

- ex_cmds.c
- misc1.c
- ops.c