updated external library versions to latest.

the configure script checks for openldap and friends and we link with those
libs just like we link all other third party libraries, and we no longer
dlopen() those libraries. Our private header file lib/ldap.h was renamed to
lib/curl_ldap.h due to this. I set a tag in CVS (curl-7_17_0-preldapfix)
just before this commit, just in case.

fixed link order in case libssh2 is build with zlib.

added defines for setlocale().

some more minor Makefile tidyups.

added distclean target.

as appropriate for platforms that don't have autotools support