nginx updates added

[Oleg Vinichenko]

nginx-1.12.2 now added. This ebuild has number of corrections in it's configure as well as adding support for stream modules, absent in older ebuild versions. This is controlled by NGINX_MODULES_STREAM expand variable, which is added into profiles. 1.12.2 version also including CVE-2017-7529 fix.

for the bleeding edge version followers, version 1.13.7 added. This ebuild has a dedicated SLOT called mainline, to follow upstream releases tags:

https://nginx.org/

and is made that it cannot be co-installed with stable versions, such as 1.12.2. This will help to distinguish the releases by upstream classification. 1.13.7 version has no keywords, it is required to unmask by keywords to be able to test.

Thanks, Oleg.