Create a private library directory (LIBPRIVATEDIR) for libraries which
we don't want to expose but which can't or shouldn't be static.

To mark a library as private, define PRIVATELIB in its Makefile.  It
will be installed in LIBPRIVATEDIR, which is normally /usr/lib/private
(or /usr/lib32/private for 32-bit libraries on 64-bit platforms).

To indicate that a program or library depends on a private library,
define USEPRIVATELIB in its Makefile.  The correct version of
LIBPRIVATEDIR will be added to its run-time library search path.

Approved by:	re (blanket)
Add a stock libmap32.conf for amd64.  The first two lines have no effect
except to document the hardcoded standard library search path for 32-bit
binaries.  The third line performs the equivalent substitution for the
private library directory.

Ironically, these entries rely on functionality which is only available
in the COMPAT_32BIT version of rtld-elf.

Approved by:	re (blanket)
Make libldns and libssh private.

Approved by:	re (blanket)