neovim.rb: modernize the style

https://github.com/styleguide/ruby
neovim.rb: improve dependency

1. remove unnecessary deps `md5sha1sum`
2. add `=> :build`
3. add missing deps `autoconf`
Merge pull request #922 'Improve neovim.rb'
Replace int with bool in some files. #654
Replaced most TRUE/FALSE macros in arabic, mbyte and spell. #645
remove proto.h include from vim.h
remove stdbool.h include from vim.h and globals.h
move memory.h include to version.c
move ascii.h include out of vim.h
move locale.h include out of vim.h
move <inttypes.h> include out of vim.h
move wctype.h include out of vim.h
move assert.h include out of vim.h
move stdarg.h include out of vim.h
move errno.h include out of vim.h
Merge #921 'Remove includes vim.h'
Fix two android compile errors in fs.c #924

Replace usage of deprecated S_IEXEC with S_IXUSR.
Rename a variable named "errno" to avoid clashing with define.
Check dependencies for each lua interpreter

- When USE_BUNDLED=OFF and the system has multiple lua interpreters
  (luajit AND lua) it may occur that only the later has the needed
  dependencies (lua-lpeg, lua-cmsgpack). If we pick luajit then
  finding the dependencies FAILS.
- This commit groups detection of the lua interpreter with the lua
  dependencies it tries to find them for both the interpreters and
  choses the first one that has them.
Refactor lua check into new cmake function

- CMake function check_lua_deps to check if lua has all dependencies
- cmake -DLUA_PRG= is now working again and is passed against
  check_lua_deps
Refactor luadeps