continuation of #109595
pkgconfig was aliased in 2018, however, it remained in
all-packages.nix due to its wide usage. This cleans
up the remaining references to pkgs.pkgsconfig and
moves the entry to aliases.nix.
python3Packages.pkgconfig remained unchanged because
it's the canonical name of the upstream package
on pypi.
Also, in case of collectd, the -lgcc_s shouldn't be needed anymore,
as the library is in ${glibc}/lib/ now, which is practically always on RPATH.
In case of seyren it was some stdenv change uncovering the mistake of
putting src into buildInputs.
source regions which are substituded by the tool nix-repository-manager.
See http://github.com/MarcWeber/nix-repository-manager/raw/master/README.
sourceByName is called sourceFromHead now.
updates: MPlayerTrunk, haxe, neko, netsurf, cinelerra, ctags
cinelerra does no longer build due to Xorg update
svn path=/nixpkgs/trunk/; revision=18894