add -fvisibility=hidden to CC flags, mark XXX_main functions

EXTERNALLY_VISIBLE. 5% size reduction of libbusybox.so

procps/free.c

@@ -11,7 +11,7 @@
 
 #include "libbb.h"
 
-int free_main(int argc, char **argv);
+int free_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int free_main(int argc, char **argv)
 {
 	struct sysinfo info;

procps/fuser.c

@@ -316,7 +316,7 @@ static int fuser_kill_pid_list(pid_list *plist, int sig)
 	return success;
 }
 
-int fuser_main(int argc, char **argv);
+int fuser_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int fuser_main(int argc, char **argv)
 {
 	/*static -- huh???*/ int opt = 0; /* FUSER_OPT_ */

procps/kill.c

@@ -24,7 +24,7 @@
  * This is needed to avoid collision with kill -9 ... syntax
  */
 
-int kill_main(int argc, char **argv);
+int kill_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int kill_main(int argc, char **argv)
 {
 	char *arg;

procps/nmeter.c

@@ -770,7 +770,7 @@ static init_func *const init_functions[] = {
 	init_cr
 };
 
-int nmeter_main(int argc, char **argv);
+int nmeter_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int nmeter_main(int argc, char **argv)
 {
 	char buf[32];

procps/pgrep.c

@@ -44,7 +44,7 @@ static void act(unsigned pid, char *cmd, int signo, unsigned opt)
 		kill(pid, signo);
 }
 
-int pgrep_main(int argc, char **argv);
+int pgrep_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int pgrep_main(int argc, char **argv)
 {
 	unsigned pid = getpid();

procps/pidof.c

@@ -16,7 +16,7 @@ enum {
 	OPT_OMIT   = USE_FEATURE_PIDOF_OMIT(  (1<<OPTBIT_OMIT  )) + 0,
 };
 
-int pidof_main(int argc, char **argv);
+int pidof_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int pidof_main(int argc, char **argv)
 {
 	unsigned first = 1;

procps/ps.c

@@ -278,7 +278,7 @@ static void format_process(const procps_status_t *ps)
 	printf("%.*s\n", terminal_width, buffer);
 }
 
-int ps_main(int argc, char **argv);
+int ps_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int ps_main(int argc, char **argv)
 {
 	procps_status_t *p;
@@ -340,7 +340,7 @@ int ps_main(int argc, char **argv)
 #else /* !ENABLE_DESKTOP */
 
 
-int ps_main(int argc, char **argv);
+int ps_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int ps_main(int argc, char **argv)
 {
 	procps_status_t *p = NULL;

procps/renice.c

@@ -26,7 +26,7 @@ void BUG_bad_PRIO_PROCESS(void);
 void BUG_bad_PRIO_PGRP(void);
 void BUG_bad_PRIO_USER(void);
 
-int renice_main(int argc, char **argv);
+int renice_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int renice_main(int argc, char **argv)
 {
 	static const char Xetpriority_msg[] ALIGN1 = "%cetpriority";

procps/sysctl.c

@@ -59,7 +59,7 @@ static void dwrite_str(int fd, const char *buf)
 /*
  *    sysctl_main()...
  */
-int sysctl_main(int argc, char **argv);
+int sysctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int sysctl_main(int argc, char **argv)
 {
 	int retval = 0;

procps/top.c

@@ -782,7 +782,7 @@ enum {
 		| PSSCAN_COMM,
 };
 
-int top_main(int argc, char **argv);
+int top_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int top_main(int argc, char **argv)
 {
 	int count, lines, col;

procps/uptime.c

@@ -25,7 +25,7 @@
 #define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
 
 
-int uptime_main(int argc, char **argv);
+int uptime_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int uptime_main(int argc, char **argv)
 {
 	int updays, uphours, upminutes;

procps/watch.c

@@ -23,7 +23,7 @@
 //
 // (procps 3.x and procps 2.x are forks, not newer/older versions of the same)
 
-int watch_main(int argc, char **argv);
+int watch_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int watch_main(int argc, char **argv)
 {
 	unsigned opt;