vcs-svn: avoid using ls command twice

vcs-svn: avoid using ls command twice

Currently there are two functions to retrieve the mode and content
at a path:

	const char *repo_read_path(const uint32_t *path);
	uint32_t repo_read_mode(const uint32_t *path)

Replace them with a single function with two return values.  This
means we can use one round-trip to get the same information from
fast-import that previously took two.

Signed-off-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>