unix: Clean up includes.

Remove unnecessary includes. Add includes that improve portability.

unix/file.c

-#include <string.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 
 #include "nlr.h"
 #include "misc.h"

unix/gccollect.c

-#include <stdint.h>
 #include <stdio.h>
 
 #include "misc.h"

unix/main.c

 #include <stdint.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 
 #include "nlr.h"
 #include "misc.h"
@@ -391,8 +394,6 @@ int main(int argc, char **argv) {
     return 0;
 }
 
-#include <sys/stat.h>
-
 uint mp_import_stat(const char *path) {
     struct stat st;
     if (stat(path, &st) == 0) {

unix/socket.c

@@ -2,7 +2,10 @@
 #include <assert.h>
 #include <string.h>
 #include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <sys/socket.h>
+#include <netinet/in.h>
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <errno.h>

unix/time.c

+#include <unistd.h>
 #include <string.h>
 #include <time.h>
 #include <sys/time.h>