x11/lightdm: Fix login.conf issues, import various improvements

• Add patch to use setusercontext(3) to setup user environment, so it respects login.conf among other things [1]
• Use autoreconf, since patch requires regenerating configure script to check for setusercontext(3) [2]
• Explicitly disable libaudit support, not supported in FreeBSD [3]
• Add QT5 options, disabled by default, to control linking against qt5 [4]
• Import patch adding option to enable alternative location for .xsession-errors file [5]
• Correctly define runtime dependencies
• Forcibly disable installation of apparmor files
• Install PAM configuration files as samples, so in the future they are not overwritten if customized
• Pet portclippy/portfmt
• Regenerate patches

Upstreaming:

[1] https://github.com/canonical/lightdm/pull/334

[5] https://github.com/canonical/lightdm/pull/335

Many thanks to all people involved!

PR: 266532 [1] [2],

		273720 [1],
		275885 [3] [4] [5]

Tested by: Ivan Rozhuk <rozhuk.im@gmail.com>,

		Daniel Tameling <tamelingdaniel@gmail.com> (provided setusercontext patch),
		Anton Saietskii <vsasjason@gmail.com>