windows-nat: Also ignore ERROR_INVALID_HANDLE from SuspendThread()

windows-nat: Also ignore ERROR_INVALID_HANDLE from SuspendThread()

Discussed somewhat in the thread at
https://cygwin.com/ml/gdb-patches/2013-06/msg00680.html

This is pretty straightforward to demonstrate on Cygwin currently:

$ cat main.c

int main()
{
  return 0;
}

$ gcc -g -O0 main.c -o main

$ ./gdb ./main
[...]
(gdb) r
Starting program: /wip/binutils-gdb/build.x86_64/gdb/main
warning: SuspendThread (tid=0x1cf0) failed. (winerr 6)
[Inferior 1 (process 976) exited normally]

with this patch applied:

$ ./gdb ./main
[...]
(gdb) r
Starting program: /wip/binutils-gdb/build.x86_64/gdb/main
[Inferior 1 (process 4852) exited normally]

gdb/ChangeLog:

2015-06-03  Jon Turney  <jon.turney@dronecode.org.uk>

	* windows-nat.c (thread_rec): Also ignore ERROR_INVALID_HANDLE
	from SuspendThread().

Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>