Remove -Werror=implicit-function-declaration, which when passed to cmake
for webkit build breaks C++ compiler configuration due to spurious warnings:
`cc1plus: warning: '-Werror=' argument '-Werror=implicit-function-declaration' is not valid for C++`
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.
After making `ffmpeg` point to the latest `ffmpeg_4`, all packages that
used `ffmpeg` without requiring a specific version now use ffmpeg_3
explicitly so they shouldn't change.
* increase heap size for building javadoc (this is only needed for the
32-bit build)
* filter out some non-maven jars that crop up in the openjfx build
