This removes the use of <config.h> from the files in gdb/nat/.
gdb/ChangeLog
2020-01-14 Tom Tromey <tom@tromey.com>
* nat/linux-btrace.c: Don't include <config.h>.
* nat/linux-ptrace.c: Don't include <config.h>.
* nat/x86-linux-dregs.c: Don't include <config.h>.
Change-Id: Ie8c734c54ada848aa020c77ec727704d367eff81