Trivial build fixes for addpartial

[Buchan Milne <bgmilne@staff.telkomsa.net>]

I should have reported this when I first enabled addpartial (but it was most 
likely near distribution release time ...), but I had patched the Makefile to 
build more sanely:

http://svn.mandriva.com/cgi-
bin/viewvc.cgi/packages/cooker/openldap/current/SOURCES/openldap-2.4.8-
addpartial-makefile.patch?revision=189682&view=markup

Since some things have now been fixed (but others not), I had to re-diff to 
address the outstanding items:

1)-fPIC is required in LDFLAGS to build on x86_64
(I didn't check to see if there's a more portable way)

2)I don't see a reason to call the overlay addpartial-overlay, we all know it 
is an overlay.

http://svn.mandriva.com/cgi-
bin/viewvc.cgi/packages/cooker/openldap/current/SOURCES/openldap-2.4.8-
addpartial-makefile.patch?revision=293664&view=markup

Regards,
Buchan