fix !ENABLE_FEATURE_GETOPT_LONG build. Closes 3775

When compiling with !ENABLE_FEATURE_GETOPT_LONG, busybox still tries
to include getopt.h which is not available; for example with uClibc
when !UCLIBC_HAS_GETOPT_LONG.  getopt.h is only required
for the _long set of functions.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

docs/style-guide.txt

@@ -679,11 +679,10 @@ line in the midst of your #includes, if you need to parse long options:
 
 Then have long options defined:
 
-	static const struct option <applet>_long_options[] = {
-		{ "list",    0, NULL, 't' },
-		{ "extract", 0, NULL, 'x' },
-		{ NULL, 0, NULL, 0 }
-	};
+	static const char <applet>_longopts[] ALIGN1 =
+		"list\0"    No_argument "t"
+		"extract\0" No_argument "x"
+	;
 
 And a code block similar to the following near the top of your applet_main()
 routine:
@@ -691,7 +690,7 @@ routine:
 	char *str_b;
 
 	opt_complementary = "cryptic_string";
-	applet_long_options = <applet>_long_options; /* if you have them */
+	applet_long_options = <applet>_longopts; /* if you have them */
 	opt = getopt32(argc, argv, "ab:c", &str_b);
 	if (opt & 1) {
 		handle_option_a();

libbb/getopt32.c

@@ -7,7 +7,9 @@
  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
 
+#if ENABLE_LONG_OPTS || ENABLE_FEATURE_GETOPT_LONG
 # include <getopt.h>
+#endif
 #include "libbb.h"
 
 /*      Documentation

selinux/chcon.c

@@ -40,7 +40,6 @@
 //usage:     "\n	-R	Recurse"
 //usage:	)
 
-#include <getopt.h>
 #include <selinux/context.h>
 
 #include "libbb.h"

selinux/runcon.c

@@ -50,7 +50,6 @@
 //usage:     "\n	-l RNG	Levelrange"
 //usage:	)
 
-#include <getopt.h>
 #include <selinux/context.h>
 #include <selinux/flask.h>
 

util-linux/getopt.c

@@ -25,7 +25,7 @@
  *   Added NLS support (partly written by Arkadiusz Mickiewicz
  *     <misiek@misiek.eu.org>)
  * Ported to Busybox - Alfred M. Szmidt <ams@trillian.itslinux.org>
- *  Removed --version/-V and --help/-h in
+ *  Removed --version/-V and --help/-h
  *  Removed parse_error(), using bb_error_msg() from Busybox instead
  *  Replaced our_malloc with xmalloc and our_realloc with xrealloc
  *
@@ -79,7 +79,9 @@
 //usage:       " esac\n"
 //usage:       "done\n"
 
+#if ENABLE_FEATURE_GETOPT_LONG
 # include <getopt.h>
+#endif
 #include "libbb.h"
 
 /* NON_OPT is the code that is returned when a non-option is found in '+'