iOS: Clean up QPlatformInputContext subclass header

Implements isValid(), which should be returning true for subclasses,
and re-orders and adds Q_DECL_OVERRIDE where appropriate.

Change-Id: I03519bf674b6f7b7ccc07a7154c9a1fb9a8105f2
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@theqtcompany.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
Add missing host_build CONFIG for qlalr

Change-Id: I6eddd2afd9eb4dac0b28329003dbd3b6d05d3fd1
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
Don't say "Neon... auto" when ARM Neon isn't detected

Just say "no".

Change-Id: I382d612ad0a7f4031b1891e7e4d9158db07badf1
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>