Add system(NULL) to fileio

[Nathan Sidwell]

Nathan Sidwell wrote:

> ------------------------------------------------------------------------
> 
> 2006-06-09  Nathan Sidwell  <nathan@codesourcery.com>
> 
> 	gdb/
> 	* remote-file.io.c (remote_fileio_func_system): Treat zero length
> 	string as NULL.  Adjust for NULL pointer argument.
> 	* doc/gdb.texinfo (system): Document behaviour with zero length
> 	string.
> 
> 	gdb/testsuite/
> 	* gdb.base/fileio.c: Add system(NULL) test.
> 	* gdb.base/fileio.exp: Check it.

I applied the patch with the suggested changes to documentation and comment. 
Daniel pointed out that I'd misunderstood Eli's email as only approving the 
documentation change, but he has told me the patch is good.

nathan
-- 
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