isatty: Make it return true in Cygwin consoles on native Windows. * lib/isatty.c: Include <string.h>. (GetProcAddress): New macro. (GetNamedPipeClientProcessIdFuncType): New type. (GetNamedPipeClientProcessIdFunc): New variable. (QueryFullProcessImageNameFuncType): New type. (QueryFullProcessImageNameFunc): New variable. (initialized): New variable. (initialize): New function. (IsCygwinConsoleHandle): New function. (isatty): Invoke it. * doc/posix-functions/isatty.texi: Mention the issue.

#!/bin/sh

tmpfile=
trap 'rm -fr $tmpfile' 1 2 3 15

tmpfile=test-fpending.t

${CHECKER} ./test-fpending${EXEEXT} > $tmpfile || exit 1

rm -fr $tmpfile

exit 0