tempname: resync from glibc

tempname: resync from glibc

* lib/tempname.c (__gen_tempname): Add suffixlen argument.  Use
same values for __GT_FILE as glibc.  Abort even when assertions
are disabled.
* lib/tempname.h (GT_FILE): Use glibc __GT_FILE, if available, and
match its value otherwise.  Allow idempotent inclusion.
* lib/mkdtemp.c (mkdtemp): Adjust caller.
* lib/mkostemp.c (mkostemp): Likewise.
* lib/mkstemp.c (mkstemp): Likewise.
* lib/tmpfile.c (tmpfile): Likewise.
* NEWS: Document this.

Signed-off-by: Eric Blake <ebb9@byu.net>