...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.
In order to not have the offending local _ZNSs4_Rep20_S_empty_rep_storageE
symbol in libguesslanglo.so, build both it and libexttextcat
with hidden visibility.
