* path.h (class path_conv): Convert path from char array to char *.

	* path.h (class path_conv): Convert path from char array to char *.
	Initialize to NULL in constructors.  Drop normalized_path_size member.
	(path_conv::size): Remove.
	(path_conv::operator =): Always copy with sizeof path_conv.  Always
	duplicate path on cygheap.
	(path_conv::set_path): Move implementation to spawn.cc.
	* path.cc (path_conv::set_normalized_path): Always allocate
	normalized_path on cygheap.
	(path_conv::check): Don't work on path, rather allocate THIS_path in
	TLS and use it throughout.  When finished, allocate path on cygheap
	and copy over.  Defer tacking on extension after having copied path.
	* spawn.cc (path_conv::set_path): Implement here.