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.
Add helper cstr_as_string()

- Add nocopy helper alternative to cstr_to_string
Refactor vim_feedkeys and f_feedkeys

- To clean up the mix between feedkeys and replace_termcodes
  the vim_feedkeys API functions now does the same thing as the
  vimscript feedkeys() function
- The original f_feedkeys() function now calls the vim_feedkeys()
  function from the API
Add API vim_replace_termcodes

- Add API function to call replace_termcodes