I suggest to try the search pattern "\<_(?:(?:_(.*))|([A-Z]+))" on source files. A couple of places will be found where names begin with two underscores or an underscore and an uppercase letter.
Examples:
- _ACCESS_H_
- _VISIBILITY_H_
http://sourceforge.net/projects/keystone/files/keystone/keystone-0.0.8.6/keystone-0.0.8.6.tar.bz2/download
This does not fit to the expected naming conventions of the C/C++ language standard.
https://www.securecoding.cert.org/confluence/display/seccode/DCL37-C.+Do+not+use+identifiers+that+are+reserved+for+the+implementation