lo-pack-sources: allow to generate .xz source tarballs by default
lo-pack-sources: allow to generate .xz source tarballs by default

Add --bzip2 and --xz options to select the compression. Both options
can be used togetger to generate both types of tarballs in one call.
XZ compession is used by default.

Also renamed "lo*build" strings to "lo*core" to fit the current name
of the top level source directory.

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core