* exception.h (exception::handler_installed): Remove.
	(exception::exception): Remove old code.  Manually install SEH handler
	instead.
	(exception::~exception): For x86_64, define frame end label.
	* exceptions.cc (exception::handler_installed): Remove.
	* libc/include/time.h (__TM_GMTOFF): Define on Cygwin.
	(__TM_ZONE): Ditto.
	(struct tm): Add __TM_GMTOFF and __TM_ZONE members if they are defined.
	* localtime.cc: Define TM_GMTOFF and TM_ZONE based on __TM_GMTOFF and
	__TM_ZONE being defined.  Throughout, write to these struct tm members
	only if CYGWIN_VERSION_CHECK_FOR_EXTRA_TM_MEMBERS is true.
	* libc/strptime.cc: Ditto.
	* include/cygwin/version.h (CYGWIN_VERSION_CHECK_FOR_EXTRA_TM_MEMBERS):
	Define.
	(CYGWIN_VERSION_API_MINOR): Bump to 272.
	* libc/include/time.h (__TM_GMTOFF): Remove Cygwin-specific definition.
	(__TM_ZONE): Ditto.
	* include/cygwin/config.h (__TM_GMTOFF): Define.
	(__TM_ZONE): Define.
	* ldap.cc (rediscover_thread): Remove.
	(cyg_ldap::open): Remove code to rediscover DC.  It just won't do the
	right thing.
	(cyg_ldap::enumerate_ad_accounts): Change to be self-sufficient (no
	explicit open call required).  Enumerate on a DC of the domain itself
	instead of relying on delegation.  Remove ill-advised code trying to
	generate rootdse from domain name.
	* passwd.cc (pg_ent::enumerate_ad): Drop explicit call to
	cyg_ldap::open.