in fcntl, avoid passing pointer arguments to syscalls as longs

really, fcntl should be changed to use the correct type corresponding
to cmd when calling va_arg, and to carry the correct type through
until making the syscall. however, this greatly increases binary size
and does not seem to offer any benefits except formal correctness, so
I'm holding off on that change for now.

the minimal changes made in this patch are in preparation for addition
of the x32 port, where the syscall macros need to know whether their
arguments are pointers or integers in order to properly pass them to
the 64-bit kernel.

src/fcntl/fcntl.c

@@ -13,11 +13,11 @@ int fcntl(int fd, int cmd, ...)
 	arg = va_arg(ap, long);
 	va_end(ap);
 	if (cmd == F_SETFL) arg |= O_LARGEFILE;
-	if (cmd == F_SETLKW) return syscall_cp(SYS_fcntl, fd, cmd, arg);
+	if (cmd == F_SETLKW) return syscall_cp(SYS_fcntl, fd, cmd, (void *)arg);
 	if (cmd == F_GETOWN) {
 		struct f_owner_ex ex;
 		int ret = __syscall(SYS_fcntl, fd, F_GETOWN_EX, &ex);
-		if (ret == -EINVAL) return __syscall(SYS_fcntl, fd, cmd, arg);
+		if (ret == -EINVAL) return __syscall(SYS_fcntl, fd, cmd, (void *)arg);
 		if (ret) return __syscall_ret(ret);
 		return ex.type == F_OWNER_PGRP ? -ex.pid : ex.pid;
 	}
@@ -37,5 +37,14 @@ int fcntl(int fd, int cmd, ...)
 		if (ret >= 0) __syscall(SYS_fcntl, ret, F_SETFD, FD_CLOEXEC);
 		return __syscall_ret(ret);
 	}
-	return syscall(SYS_fcntl, fd, cmd, arg);
+	switch (cmd) {
+	case F_SETLK:
+	case F_SETLKW:
+	case F_GETLK:
+	case F_GETOWN_EX:
+	case F_SETOWN_EX:
+		return syscall(SYS_fcntl, fd, cmd, (void *)arg);
+	default:
+		return syscall(SYS_fcntl, fd, cmd, arg);
+	}
 }