More fixes for Betriebssystemschwein

Set _X_OPEN_SOURCE=600 and -std=c99 earlier so that ./configure runs against appropriate versions of the POSIX APIs.

Fix rlm_krb5 configure script to correctly detect that Betriebssystemschwein's libkrb5 is based on MIT's

Include fcntl.h in log.c, this should probably always of been included...

Add alternative names for macros in rlm_ldap/ldap.h and #ifdef out a few lines of code, as starttls doesn't seen to be available...