libobjcryst is now built from a release tag.

No need for special cleanup rules.
Add src-addons directory for extra src files.

These files are copied over to the src/ tree once all sources are
downloaded.
Simply ignore whole generated src tree.
Set RPATH when linking rather than with patchelf.
Set RPATH with linker instead of running patchelf.
Away with patchelf!  noweb is also not needed.