* uinfo.cc (pwdgrp::fetch_account_from_windows): Drop "plus_prepended"
	as naming style.  Drop enum name_style_t, use a boolean
	"fully_qualified_name" value instead.  Rework function to drop
	"plus_prepended" handling througout and default to "name only" style
	as replacement.
	* uinfo.cc (pwdgrp::fetch_account_from_windows): Drop "plus_prepended"
	as naming style.  Drop enum name_style_t, use a boolean
	"fully_qualified_name" value instead.  Rework function to drop
	"plus_prepended" handling througout and default to "name only" style
	as replacement.
	* common.din (__cxa_atexit): Export.
	* include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Bump to 274.
	* common.din (__cxa_atexit): Export.
	* include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Bump to 274.
	* libc/include/math.h: Also define M_PI etc. if _XOPEN_SOURCE is
	defined appropriately.