main.c (main): If we are resizing a plain file which is smaller

main.c (main): If we are resizing a plain file which is smaller
	than the requested size, then we will attempt to
	transparently extend the filesize in a sparse fashion by
	writing a block at the end of the requested part of the
	filesystem.

main.c (main), resize2fs.c (resize_fs), resize2fs.h: Change the
	function prototype of resize_fs() so that it can modify
	the new_size parameter with the actual new size of the
	filesystem after the resize operation.  (This can
	sometimes be less than the requested new size if there
	isn't enough space to create the necessary block group
	metadata for that last bit of disk space.)  Resize2fs now
	prints the actual new size of the filesystem when it finishes.