Add new GCC 9 warnings to warnings.m4

Add new GCC 9 warnings to warnings.m4

GCC 9 has a few new warnings that aren't enabled in the gdb build by
default: -Wdeprecated-copy, -Wdeprecated-copy-dtor, and
-Wredundant-move.  This patch enables them all.

Tested by rebuilding with a new GCC (git master) on x86-64 Fedora 29.

gdb/ChangeLog
2019-05-29  Tom Tromey  <tromey@adacore.com>

	* inflow.c (struct terminal_info): Add default operator=.
	* configure: Rebuild.
	* warning.m4 (AM_GDB_WARNINGS): Add -Wdeprecated-copy,
	-Wdeprecated-copy-dtor, -Wredundant-move.

gdb/gdbserver/ChangeLog
2019-05-29  Tom Tromey  <tromey@adacore.com>

	* configure: Rebuild.