Scatter output hook

This hook allows to scatter files in $out to multiple outputs.
For "bin" and "doc" outputs there are prefefined default masks, but
they can be overriden by setting files_<outname>, for example:

files_bin = [ "/bin/*" "/lib/libexec/" ];

To make an effect hook must be specified in buildInputs.
make use of new extractRuntimeHook
Don't hardcode shell, use $SHELL instead
Merge pull request #2063 from redbaron/libmsgpack

Proper separation between build and runtime outputs