tree-wide: change option_parse() to return option and arg via internal state

It was requested to make the 'c', 'opt', and 'arg' params the same, i.e.
defined through the FOREACH_OPTION macro. But we can't do that easily,
because 'c' was defined in the for loop definition, and we can only
define variables of the same type in that way. Also, in some cases we
need only 'c', in other cases with need 'c' and 'arg, in some cases 'c'
and 'opt', and in other cases all three. We'd need to either
conditionalize or mark those variables with _unused_ to deal with
compiler warnings. But a different approach works quite nicely: add
state.opt and state.arg to show the current option and it's argument.
(The short names are picked on purpose to reduce verbosity since those
are used a lot.)

src/cryptsetup/cryptsetup.c

@@ -2505,10 +2505,9 @@ static int parse_argv(int argc, char *argv[], char ***ret_args) {
         assert(argv);
         assert(ret_args);
 
-        OptionParser state = { argc, argv };
-        const char *arg;
+        OptionParser opts = { argc, argv };
 
-        FOREACH_OPTION(&state, c, &arg, /* on_error= */ return c)
+        FOREACH_OPTION(c, &opts, /* on_error= */ return c)
                 switch (c) {
 
                 OPTION_COMMON_HELP:
@@ -2518,7 +2517,7 @@ static int parse_argv(int argc, char *argv[], char ***ret_args) {
                         return version();
                 }
 
-        *ret_args = option_parser_get_args(&state);
+        *ret_args = option_parser_get_args(&opts);
         return 1;
 }