* faq-what.xml (faq.what.who): CGF has retired.
headers: properly decorate attributes

Found by:
find -name '*.h' |xargs grep -i 'attribute.*(([a-z]'

For an example of the type of bugs this causes, try compiling this valid
C11 program (it's valid because 'noreturn' is reserved for use in the
user namespace unless you include <stdnoreturn.h>):

$ cat foo.c
#define noreturn __attribute__((noreturn))
#include <stdlib.h>
$ gcc -c -o foo.o -Wall foo.c
In file included from /usr/include/stdlib.h:11:0,
                 from foo.c:2:
foo.c:1:18: error: expected ')' before '__attribute__'
 #define noreturn __attribute__((noreturn))
                  ^
/usr/include/stdlib.h:66:28: error: expected ',' or ';' before ')' token
 _VOID _EXFUN(abort,(_VOID) _ATTRIBUTE ((noreturn)));
                            ^

* libc/machine/spu/spu_timer_internal.h: Decorate attribute names
with __, for namespace safety.
* libc/machine/xscale/machine/profile.h: Likewise.
* libc/include/stdlib.h: Likewise.
* libc/include/_ansi.h: Likewise.
* libc/include/sys/unistd.h: Likewise.
* libc/sys/linux/linuxthreads/libc-symbols.h: Likewise.
* libc/sys/linux/linuxthreads/internals.h: Likewise.
* libc/sys/linux/machine/i386/weakalias.h: Likewise.
* libc/sys/linux/machine/i386/dl-procinfo.h: Likewise.
* libc/sys/linux/machine/i386/dl-machine.h: Likewise.
* libc/sys/linux/libc-symbols.h: Likewise.
* libc/sys/linux/iconv/gconv_charset.h: Likewise.
* libc/sys/linux/include/resolv.h: Likewise.
* libc/sys/linux/sys/unistd.h: Likewise.
* libc/sys/linux/dl/atomicity.h: Likewise.
* libc/sys/linux/dl/dynamic-link.h: Likewise.
* libc/sys/linux/dl/ldsodefs.h: Likewise.
headers: properly decorate attributes

As pointed out here:
https://cygwin.com/ml/cygwin/2014-07/msg00371.html

any use of __attribute__ in a header that can be included by a user
should be namespace-safe, by decorating the attribute arguments with __
(while gcc does a lousy job at documenting it, ALL attributes have a __
counterpart, precisely so that public headers can use attributes without
risk of collision with macros belonging to user namespace).

* include/pthread.h: Decorate attribute names with __, for
namespace safety.
* include/cygwin/core_dump.h: Likewise.
* include/cygwin/cygwin_dll.h: Likewise.
* include/sys/cygwin.h: Likewise.
* include/sys/strace.h: Likewise.
* faq-what.xml (faq.what.who): Remove mention of retired setup
maintainers.  Add link to cygwin-pkg-maint.
	* 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.
	* libc/include/math.h: Also define M_PI etc. if _XOPEN_SOURCE is
	defined appropriately.
	* include/sys/file.h: Add extern "C".
	* ntsec.xml (ntsec-mapping): Drop plus-prepended builtin accounts as
	default setting.  Add short explanation in db_prefix: always mode.
	Fix a type.  Drop a paragraph with redundant information.
	* passwd.c (usage): Rename DAYS to MINDAYS and MAXDAYS.
	* utils.xml (passwd): Ditto.
* Makefile.common (COMPILE.cc): Add -fno-use-cxa-atexit.
* common.din (__cxa_finalize): Export.
* dcrt0.cc (cygwin_atexit): Use d->handle with __cxa_atexit.
* dll_init.cc (dll_list::detach): Use d->handle with __cxa_finalize.
* include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Use 274 for
__cxa_finalize as well.
Merge branch 'Cygwin' into develop