.gitignore /.gdb_history

Change-Id: I254c0104010cc1a1c12bbf1af048966de66924e6
Reviewed-on: https://gerrit.libreoffice.org/10973
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>