objcopy: Get input file stat after BFD open

objcopy: Get input file stat after BFD open

Get file state from the descriptor opened by copy_file for the input
BFD.  This ensures continuity in the view of the input file through
the descriptor.  At the moment it is only to preserve timestamps
recorded at the point that we opened the file for input but in the
next patch this state will also be used to preserve ownership and
permissions wherever applicable.

binutils/

	* objcopy.c (copy_file): New argument IN_STAT.  Return stat of
	ibfd through it.
	(strip_main): Remove redundant stat calls.  adjust copy_file
	calls.
	(copy_main): Likewise.