Update ctime_r() argument macro to cache results and to produce

one preprocessor macro instead of two.  Ran aclocal, autoconf,
autoheader to update derived files.  Modify util-int.c to use
CTIME_R_NARGS define and fallback to ctime() if not set.
Made LDAP_API_FEATURE_X_OPENLDAP_REENTRANT dependent upon result.