Rename aux.c to auxv.c.

On Windows, AUX is the auxiliary device, usually pointing to COM1.
Therefore it is forbidden to create a file named aux.c. To make it a bit
easier for Windows users to check out our source code, rename this file
to auxv.c.

MFC after:	1 month
Discussed with:	kib
Suggested by:	Eric van Gyzen <eric vangyzen net>

lib/libc/gen/Makefile.inc

@@ -7,7 +7,7 @@
 SRCS+=  __getosreldate.c __xuname.c \
 	_once_stub.c _pthread_stubs.c _rand48.c _spinlock_stub.c \
 	_thread_init.c \
-	alarm.c arc4random.c assert.c aux.c basename.c check_utility_compat.c \
+	alarm.c arc4random.c assert.c auxv.c basename.c check_utility_compat.c \
 	clock.c closedir.c confstr.c \
 	crypt.c ctermid.c daemon.c devname.c dirfd.c dirname.c disklabel.c \
 	dlfcn.c drand48.c elf_utils.c erand48.c err.c errlst.c errno.c \