Switch to POSIXLY_CORRECT mode for getopt_long()

This  makes the  first non-option  argument end  getopt_long() parsing
stop rather  than shuffling non-option  arguments to the end.  This is
necessary  so that  rig/rotator command  language arguments  can start
with a  '-' character and  also it enables  the '-' pseudo  command to
switch to reading commands from stdin work correctly.

The change  also make checking for  the '-', switch to  stdin, command
stricter in that it must be where a command is expected and it must be
a word containing exactly a single '-' character.

Overall this allows the following styles of use:

$ rigctl R -

$ rigctl - <<EOF
>R -
>EOF

R -

$ echo "R -" | rigctl -

R -
$ rigctl -m 1 M CW -1

$ rigctl F 434000000 - <<EOF
>M FM 15000
>f m
>EOF

M FM 15000
f 145000000

m FM
15000

$

as well  as the command  line interpreter operation where  no commands
nor '-' are provided:

$ rigctl

Rig command: R -

Rig command: r
Rptr Shift: -

Rig command: f
Frequency: 145000000

Rig command: m
Mode: FM
Passband: 15000

Rig command: F 434000000

Rig command: f
Frequency: 434000000

Rig command: q

$

tests/rigctl.c

@@ -87,7 +87,7 @@ void usage(void);
  * NB: do NOT use -W since it's reserved by POSIX.
  * TODO: add an option to read from a file
  */
-#define SHORT_OPTIONS "m:r:p:d:P:D:s:c:t:lC:LuonvhV"
+#define SHORT_OPTIONS "+m:r:p:d:P:D:s:c:t:lC:LuonvhV"
 static struct option long_options[] =
 {
 	{"model",           1, 0, 'm'},

tests/rigctl_parse.c

@@ -452,7 +452,7 @@ static int next_word (char *buffer, int argc, char *argv[], int newline)
   if (!reading_stdin)
     {
       if (optind >= argc) return EOF;
-      else if ('-' == argv[optind][0])
+      else if (newline && '-' == argv[optind][0] && 1 == strlen (argv[optind]))
         {
           ++optind;
           reading_stdin = 1;

tests/rotctl.c

@@ -82,7 +82,7 @@ void usage();
  * NB: do NOT use -W since it's reserved by POSIX.
  * TODO: add an option to read from a file
  */
-#define SHORT_OPTIONS "m:r:s:C:t:LvhVlu"
+#define SHORT_OPTIONS "+m:r:s:C:t:LvhVlu"
 static struct option long_options[] =
 {
 	{"model",    1, 0, 'm'},

tests/rotctl_parse.c

@@ -354,7 +354,7 @@ static int next_word (char *buffer, int argc, char *argv[], int newline)
   if (!reading_stdin)
     {
       if (optind >= argc) return EOF;
-      else if ('-' == argv[optind][0])
+      else if (newline && '-' == argv[optind][0] && 1 == strlen (argv[optind]))
         {
           ++optind;
           reading_stdin = 1;