...by allowing our special @___... tokens anywhere within an install name,
so that external modules can configure --prefix=/@___... etc.  This removes
the need for the special extshl and EXTRPATH=LOADER.  Also, a new
OUT2BIN_NONE can be used for external modules where the generated libraries
need the default EXTRPATH=OOO, but generated executables are only used
during the build and such need RPATH=NONE.