Problem:    Get_tv function names are not consistent.
Solution:   Rename to tv_get.
https://github.com/vim/vim/commit/d155d7a8519987361169459b8d464ae1caef5e9c

Only a change in comments appears to be necessary.

    In file included from ../src/nvim/eval/encode.c:974:
    ../src/nvim/eval/typval_encode.c.h:390:40: error: equality comparison with extraneous parentheses [-Werror,-Wparentheses-equality]
              do { if ((tv->vval.v_special == kSpecialVarTrue)) { msgpack_pack_true(packer); } else { msgpack_pack_false(packer); } } while (0);
                        ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~

`tv` is passed to the TYPVAL_ENCODE_CONV_FUNC_BEFORE_* macros, which
don't appear to actually use that parameter.

Found by clang scan-build 5.0

Problem:    Padding in list type wastes memory.
Solution:   Reorder struct members to optimize padding. (Dominique Pelle,
            closes vim/vim#2704)
https://github.com/vim/vim/commit/1a840240376f2858d489736f9eed6d2975225fdf

src/nvim/eval/typval.c
src/nvim/fileio.c
src/nvim/main.c
src/nvim/regexp_nfa.c
src/nvim/spellfile.c

changed some EMSG[..] Macros to emsgf

log.c
message.c
strings.c

fixed some printf warnings in:

src/nvim/undo.c
src/nvim/eval.c
src/nvim/eval/encode.c
src/nvim/eval/typval.c
src/nvim/ex_getln.c
src/nvim/fileio.c
src/nvim/lua/executor.c
src/nvim/main.c
src/nvim/regexp_nfa.c
src/nvim/shada.c
src/nvim/spellfile.c
src/nvim/tui/terminfo.c
src/nvim/garray.h

ref https://github.com/neovim/neovim/issues/9001#issuecomment-421843790

Steps to reproduce:
    :set verbose=9
    :call system(['echo'])
    E730: using List as a String

Problem:    Duplication of code for adding a list or dict return value.
Solution:   Add rettv_dict_set() and rettv_list_set(). (Yegappan Lakshmanan)
https://github.com/vim/vim/commit/45cf6e910c6d162775ca9d470fac4b6db844001f