Bug#779224: Experimental branch runs checks in parallel

[Felix Lechner <felix.lechner@lease-up.com>]

Control: retitle -1 lintian: run checks in parallel
Control: severity -1 normal

Hi,

 > * Do checks in subprocesses, so memory will be reclaimed

There is an experimental branch that runs checks in parallel. For
reasons unknown, It is slower by a factor of two or more.

Reasons may include unwanted serialization (although most data
structures were "closed upon") or a repeated reading of the remaining
collections files. Most data is now in memory, but some files remain.
There are 161 checks.

The strategy "fork, do memory intensive stuff, exit" is the best and
maybe only way to recapture memory in Perl. Running checks in parallel
would automatically release memory used in each check. Re-titling the
bug accordingly.

Kind regards
Felix Lechner