tini.c: a function declaration without a prototype is deprecated in all versions of C

| /srv/oe/build/tmp-lmp/work/corei7-64-lmp-linux/tini/0.19.0-r0/git/src/tini.c:150:18: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
| int isolate_child() {
|                  ^
|                   void
| /srv/oe/build/tmp-lmp/work/corei7-64-lmp-linux/tini/0.19.0-r0/git/src/tini.c:395:14: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
| int parse_env() {
|              ^
|               void
| /srv/oe/build/tmp-lmp/work/corei7-64-lmp-linux/tini/0.19.0-r0/git/src/tini.c:416:24: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
| int register_subreaper () {
|                        ^
|                         void
| /srv/oe/build/tmp-lmp/work/corei7-64-lmp-linux/tini/0.19.0-r0/git/src/tini.c:434:19: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
| void reaper_check () {
|                   ^
|                    void
| 4 errors generated.

Signed-off-by: Jose Quaresma <jose.quaresma@foundries.io>

src/tini.c

@@ -147,7 +147,7 @@ int restore_signals(const signal_configuration_t* const sigconf_ptr) {
 	return 0;
 }
 
-int isolate_child() {
+int isolate_child(void) {
 	// Put the child into a new process group.
 	if (setpgid(0, 0) < 0) {
 		PRINT_FATAL("setpgid failed: %s", strerror(errno));
@@ -392,7 +392,7 @@ int parse_args(const int argc, char* const argv[], char* (**child_args_ptr_ptr)[
 	return 0;
 }
 
-int parse_env() {
+int parse_env(void) {
 #if HAS_SUBREAPER
 	if (getenv(SUBREAPER_ENV_VAR) != NULL) {
 		subreaper++;
@@ -413,7 +413,7 @@ int parse_env() {
 
 
 #if HAS_SUBREAPER
-int register_subreaper () {
+int register_subreaper (void) {
 	if (subreaper > 0) {
 		if (prctl(PR_SET_CHILD_SUBREAPER, 1)) {
 			if (errno == EINVAL) {
@@ -431,7 +431,7 @@ int register_subreaper () {
 #endif
 
 
-void reaper_check () {
+void reaper_check (void) {
 	/* Check that we can properly reap zombies */
 #if HAS_SUBREAPER
 	int bit = 0;