Auto merge of #3306 - bstaletic:neovim_has_python_compiled, r=micbou

[READY] Restore neovim support

# PR Prelude

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- [x] I have read and understood YCM's [CONTRIBUTING][cont] document.
- [x] I have read and understood YCM's [CODE_OF_CONDUCT][code] document.
- [x] I have included tests for the changes in my PR. If not, I have included a
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# Why this change is necessary and useful

[Please explain **in detail** why the changes in this PR are needed.]

[cont]: https://github.com/Valloric/YouCompleteMe/blob/master/CONTRIBUTING.md
[code]: https://github.com/Valloric/YouCompleteMe/blob/master/CODE_OF_CONDUCT.md

Turns out neovim doesn't have `has('python_compiled')`, so we need to check if the user is running neovim before checking `has('python_compiled')`.

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plugin/youcompleteme.vim

@@ -54,7 +54,8 @@ elseif !has( 'timers' )
         \ echohl None
   call s:restore_cpo()
   finish
-elseif !has( 'python_compiled' ) && !has( 'python3_compiled' )
+elseif ( v:version > 800 || ( v:version == 800 && has( 'patch1436' ) ) ) &&
+     \ !has( 'python_compiled' ) && !has( 'python3_compiled' )
   echohl WarningMsg |
         \ echomsg "YouCompleteMe unavailable: requires Vim compiled with " .
         \ "Python (2.7.1+ or 3.4+) support." |