Add myself to gdb/MAINTAINERS

gdb/ChangeLog:

2019-04-01  Marco Barisione  <mbarisione@undo.io>

	* MAINTAINERS (Write After Approval): Add Marco Barisione.

Author: barisione

gdb/MAINTAINERS

@@ -449,6 +449,7 @@ Shrinivas Atre					shrinivasa@kpitcummins.com
 Sterling Augustine				saugustine@google.com
 John Baldwin					jhb@freebsd.org
 Scott Bambrough					scottb@netwinder.org
+Marco Barisione					mbarisione@undo.io
 Thiago Jung Bauermann				bauerman@br.ibm.com
 Jon Beniston					jon@beniston.com
 Gary Benson					gbenson@redhat.com