Some problems about completing CPP files

[ZhuJiaYou]

Hi, @maralla
I've used Completor for a period of time in VIM 8.1 on Linux Mint 19.1. And it works well with Python files.
But I've got some problems with CPP files.
I've installed clang6.0 and added let g:completor_clang_binary = '/usr/bin/clang' in my .vimrc file, besides, I've added -std=c++11 in .clang_complete in the path ~/.vim/pack/completor/start/completor.vim/ to support c++11.

1. It seems like that there're no completion candidates for include files, such as iostream, stdio.h and so on.
   
2. There're no completion candidates for some c++11 key words such as decltype, noexcept, but there're some such as auto.
   

I'm wondering whether my configrations are not correct, or there're some bugs??

[ZhuJiaYou]

In addition, it seems like that there're no completion candidates for many key words in C/C++, such as private, protected, typedef, typename, switch and so on.

[maralla]

I pushed a commit to enable some item completions, but there are still some items can not be completed. The cpp completer needs to be improved of course.