Some header file are recognized of c not c++

[jiangxianfu]

When I used the tool to parse, I found that some header files could be correctly identified as c++, but some were identified as c language. I wonder if there is a good way to avoid this.

10:38:53 indexer0 pipeline.cc:386 I parse /oceanbase/src/sql/engine/ob_exec_context.h error:3 unknown type name 'namespace'

Of course, I have also adopted the solution ideas provided by the FAQ, but the more it is used, the more chaotic it is. https://github.com/MaskRay/ccls/wiki/FAQ#some-cc-headers-are-not-recognized