Changes to setup.py and setup.cfg

[Michael Ströder]

HI!

I've checked in some changes to setup.py and setup.cfg hopefully 
simplyfing this.

1. Renamed DEFINE name HAVE_LDAP_START_TLS_S to HAVE_TLS.

2. HAVE_TLS is set by looking at line libs in setup.cfg. If it 
contains ssl *and* crypto HAVE_TLS is set. Otherwise support for 
StartTLS extended operation and LDAP over SSL is turned off.

3. I dropped support for line class in section [_ldap] of 
setup.cfg since we won't have support for other LDAP C SDKs.

Please test if these changes have any bad implications on various 
build platforms.

Ciao, Michael.