Move files from src/ to src/nvim/.
- src/nvim/ becomes the new root dir for nvim executable sources.
- src/libnvim/ is planned to become root dir of the neovim library.

If this backslash is here and USE_VALGRIND is defined, valgrind complains that "else" is not a command.

Problem:    Escaping a file name for shell commands can't be done without a
            function.
Solution:   Add the :S file name modifier.

https://code.google.com/p/vim/source/detail?r=40f18a1c1592c8b4047f6f2a413557f48a99c55f

Problem:    Parsing 'errorformat' is not correct.
Solution:   Reset "multiignore" at the start of a multi-line message. (Lcd)

https://code.google.com/p/vim/source/detail?r=fb24b025c7cf07db79a559a3091db42e02c1af86

Problem:    Fixes are not tested.
Solution:   Add a test for not autoloading on assignment. (Yukihiro Nakadaira)

https://code.google.com/p/vim/source/detail?r=22387c8eec43ea8b1b704cad49c8f7187e2fd579

The environment variable USE_VALGRIND can be set to run tests with valgrind. If
VALGRIND_GDB is set, valgrind will start it's own gdbserver for remote
debugging with `target remote | vgdb`. USE_GDB can still be used, but it will
be ignored if USE_VALGRIND is set.

This feature was accidentally removed when doing the initial import from vim. It
makes vim use pipes instead of temporary files for filtering buffers through
shell commands.

I found that this was missing when looking for references of
SHELL_READ/SHELL_WRITE outside mch_call_shell`.

When `mch_call_shell` is reimplemented on top of libuv process management
facilities, pipes will always be used for communication with child processes so
it makes sense to enable the feature permanently.