gnu packages: Clean up synopses and descriptions.

gnu packages: Clean up synopses and descriptions.

* gnu/packages/admin.scm, gnu/packages/algebra.scm, gnu/packages/audio.scm,
  gnu/packages/backup.scm, gnu/packages/base.scm, gnu/packages/bittorrent.scm,
  gnu/packages/code.scm, gnu/packages/compression.scm,
  gnu/packages/databases.scm, gnu/packages/enchant.scm,
  gnu/packages/firmware.scm, gnu/packages/fonts.scm,
  gnu/packages/freedesktop.scm, gnu/packages/games.scm, gnu/packages/gd.scm,
  gnu/packages/gl.scm, gnu/packages/gnome.scm, gnu/packages/gsasl.scm,
  gnu/packages/gstreamer.scm, gnu/packages/gtk.scm, gnu/packages/guile.scm,
  gnu/packages/haskell.scm, gnu/packages/language.scm,
  gnu/packages/lesstif.scm, gnu/packages/libreoffice.scm,
  gnu/packages/linux.scm, gnu/packages/llvm.scm, gnu/packages/maths.scm,
  gnu/packages/mcrypt.scm, gnu/packages/mit-krb5.scm, gnu/packages/mp3.scm,
  gnu/packages/ncdu.scm, gnu/packages/networking.scm, gnu/packages/ntp.scm,
  gnu/packages/ocaml.scm, gnu/packages/openbox.scm, gnu/packages/pdf.scm,
  gnu/packages/perl.scm, gnu/packages/pretty-print.scm,
  gnu/packages/pulseaudio.scm, gnu/packages/python.scm,
  gnu/packages/rdesktop.scm, gnu/packages/rdf.scm, gnu/packages/ruby.scm,
  gnu/packages/slang.scm, gnu/packages/slim.scm, gnu/packages/telephony.scm,
  gnu/packages/tls.scm, gnu/packages/tmux.scm, gnu/packages/tre.scm,
  gnu/packages/unrtf.scm, gnu/packages/version-control.scm,
  gnu/packages/vpn.scm, gnu/packages/web.scm, gnu/packages/wget.scm,
  gnu/packages/xdisorg.scm, gnu/packages/xfce.scm, gnu/packages/xiph.scm:
  Fix typos.  Trim long lines.  Add missing periods in the end of sentences.
  Use double spaces between sentences.  Remove trailing whitespaces.