Update email for Pierre Neidhardt.

Update email for Pierre Neidhardt.

* .mailmap: Add name and email for Pierre Neidhardt.
* gnu/packages/c.scm, gnu/packages/code.scm, gnu/packages/compression.scm,
gnu/packages/disk.scm, gnu/packages/emacs.scm, gnu/packages/freedesktop.scm,
gnu/packages/golang.scm, gnu/packages/image.scm, gnu/packages/music.scm,
gnu/packages/networking.scm, gnu/packages/password-utils.scm,
gnu/packages/perl-check.scm, gnu/packages/perl.scm,
gnu/packages/textutils.scm, gnu/packages/video.scm, gnu/packages/xdisorg.scm:
Update email for Pierre Neidhardt.