lib/util.sh: added unalias () override, which doesn't produce an error if the alias is undefined

bugfix: lib/util.sh: renamed echo_func () to echo_func_ (), because you apparently can't have a function with the same name as an alias, even if the function is defined before the alias and an include guard prevents the function from being defined again after the alias is set. there may be some kind of alias-expanding preprocessing pass that bash only does in script mode, or maybe there is some other problem related to our use of aliases inside if statements.

*{.sh,run}: changed echo_func to an alias that includes the "$", so that callers don't need to specify the "$" manually. although the original echo_func function is still there, callers need to switch over to the alias at the same time as it's defined because otherwise the "$@" would be doubled, since echo_func refers to the alias instead.

lib/util.sh: added set_make_vars alias, for use with make-target-style shell functions

lib/util.sh: mysql_cmd (): interpret an empty string for $user, $database as if they were unset

bugfix: lib/util.sh: mysql_cmd (): add --tables after specifying --databases so that future unnamed arguments are correctly interpreted as tables

bugfix: lib/util.sh: mysql_cmd (): need to use `--databases ...` rather than `--database=...` to specify the database as a named argument

bugfix: lib/util.sh: mysql_cmd (): need space before $database in command

lib/util.sh: mysql_cmd (): use $schema as $database when provided

lib/util.sh: mysql_cmd (): accept $database connection var