debugging.
(__set_errno): Declare when DEBUGGING.
* cygheap.h (cygheap_fdget::cygheap_fdget): Add a flag to control when errno is
set.
* debug.cc (__set_errno): New function.
* fcntl.cc (_fcntl): Fix so that correct fd is used for second argument to
dup2.
* syscalls.cc (_cygwin_istext_for_stdio): Don't set errno here when using
cygheap_fdget.