Warn on non-portable compressed doman and newman arguments

[thesamesam]

See https://bugs.gentoo.org/619916. PMS does not state that compressed doman and newman arguments must be accepted, hence relying on them in ebuilds is nonportable.

Portage warns on this (this example is at 68c2e4bfc966c7ef2154474a14c7bdc338fd53cb, app-misc/socnetv-2.2):

 * QA Notice: doman argument '/var/tmp/portage/app-misc/socnetv-2.2/work/socnetv-2.2/man/socnetv.1.gz' is compressed, this is not portable
>>> Completed installing app-misc/socnetv-2.2 into /var/tmp/portage/app-misc/socnetv-2.2/image

 * Final size of build directory: 138300 KiB (135.0 MiB)
 * Final size of installed tree:   31696 KiB ( 30.9 MiB)

 * QA Notice: One or more compressed files were found in docompress-ed
 * directories. Please fix the ebuild not to install compressed files
 * (manpages, documentation) when automatic compression is used:
 *
 *   /usr/share/man/man1/socnetv.1.gz

but pkgcheck should be able to detect it statically.

Example bad calls:

src_install() {
	[...]

	doman foo.1.gz # .gz should not be here!
	newman foo.1.gz <anything> # .gz should not be in source!
}