add missing includes of unistd.h for smallint usage

remove a few duplicate includes of unistd.h

libc/inet/netlinkaccess.h

@@ -21,6 +21,7 @@
 
 #include <features.h>
 #include <stdint.h>
+#include <unistd.h>
 #include <sys/types.h>
 
 #define _LINUX_TYPES_H

libc/misc/fnmatch/fnmatch.c

@@ -41,6 +41,7 @@
 #include <errno.h>
 #include <fnmatch.h>
 #include <ctype.h>
+#include <unistd.h>
 
 #if HAVE_STRING_H || defined _LIBC
 # include <string.h>

libc/misc/regex/regex_old.c

@@ -35,6 +35,7 @@
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
+#include <unistd.h>
 #include <malloc.h>
 #include <stdio.h>
 

libc/stdlib/malloc-simple/alloc.c

@@ -13,7 +13,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
 #include <errno.h>
 #include <sys/mman.h>
 

libc/sysdeps/linux/nios/crtend.c

@@ -1,5 +1,6 @@
 #include <errno.h>
 #include <stdlib.h>
+#include <unistd.h>
 /*
 static void (*__CTOR_END__[1]) __P((void))
     __attribute__((section(".ctors"))) = { (void *)-1 };

libc/unistd/fpathconf.c

@@ -23,7 +23,6 @@
 #include <sys/statfs.h>
 #include <errno.h>
 #include <stddef.h>
-#include <unistd.h>
 #include <limits.h>
 #include <fcntl.h>
 #include <sys/stat.h>