Everywhere: void arguments to C functions

Problem:
- C functions with no arguments require a single `void` in the argument list.

Solution:
- Put the `void` in the argument list of functions in C header files.

Libraries/LibC/stdlib.cpp

@@ -1021,7 +1021,7 @@ unsigned long long strtoull(const char* str, char** endptr, int base)
 // Serenity's PRNG is not cryptographically secure. Do not rely on this for
 // any real crypto! These functions (for now) are for compatibility.
 // TODO: In the future, rand can be made deterministic and this not.
-uint32_t arc4random()
+uint32_t arc4random(void)
 {
     char buf[4];
     syscall(SC_getrandom, buf, 4, 0);

Libraries/LibC/stdlib.h

@@ -41,13 +41,13 @@ __BEGIN_DECLS
 __attribute__((malloc)) __attribute__((alloc_size(1))) void* malloc(size_t);
 __attribute__((malloc)) __attribute__((alloc_size(1, 2))) void* calloc(size_t nmemb, size_t);
 size_t malloc_size(void*);
-void serenity_dump_malloc_stats();
+void serenity_dump_malloc_stats(void);
 void free(void*);
 __attribute__((alloc_size(2))) void* realloc(void* ptr, size_t);
 char* getenv(const char* name);
 int putenv(char*);
 int unsetenv(const char*);
-int clearenv();
+int clearenv(void);
 int setenv(const char* name, const char* value, int overwrite);
 int atoi(const char*);
 long atol(const char*);
@@ -87,7 +87,7 @@ void srand(unsigned seed);
 long int random();
 void srandom(unsigned seed);
 
-uint32_t arc4random();
+uint32_t arc4random(void);
 void arc4random_buf(void*, size_t);
 uint32_t arc4random_uniform(uint32_t);
 

Libraries/LibC/syslog.cpp

@@ -94,7 +94,7 @@ void closelog_r(struct syslog_data* data)
     data->maskpri = LOG_UPTO(LOG_DEBUG);
 }
 
-void closelog()
+void closelog(void)
 {
     closelog_r(&global_log_data);
 }

Libraries/LibC/syslog.h

@@ -169,7 +169,7 @@ void vsyslog(int, const char* message, va_list);
 void vsyslog_r(int, struct syslog_data* data, const char* message, va_list);
 void openlog(const char*, int, int);
 void openlog_r(const char*, int, int, struct syslog_data*);
-void closelog();
+void closelog(void);
 void closelog_r(struct syslog_data*);
 int setlogmask(int);
 int setlogmask_r(int, struct syslog_data*);