lib/sh/util.sh: added echo_vars() stub

lib/sh/util.sh: added echo_run() stub

lib/sh/util.sh: set_fds(): don't run (or echo) exec if no redirections are being made

bugfix: lib/sh/util.sh: added missing stub for indent alias (used by echo_func alias, which is a stub). without the stub, /usr/bin/indent would be used instead on Mac.

bugfix: lib/sh/local.sh: root_rel_path(): added echo_func

bugfix: lib/sh/local.sh: root_rel_path(): use canon_rel_path instead of rel_path because $1 may be absolute rather than relative to the current dir, so $root_dir needs to be absoluted (which requires $1 to be absoluted as well)

lib/sh/util.sh: support custom $base_dir, which will be run through realpath() to match $path ($PWD, which was used before, did not need to be realpath'd because it was already absolute)

lib/sh/util.sh: moved echo_func alias to stub because it must be embedded in its expanded alias form to work properly

lib/sh/util.sh: declare echo_func as a stub before it's defined, so that functions can use it even if they are defined before it (and its logging functionality will be enabled as soon as it's defined)

lib/sh/util.sh: rel_path(): don't log++ it, and instead only log++ applicable calls of it or its callers. this allows non-internal calls of rel_path() to be logged at the usual log_level.