e2fsck: always make sure e2fsck_global_ctx is set

The e2fsck_global_ctx varible was only being set if HAVE_SIGNAL_H is
defined.  There are systems, such as Android, where this is not true.

This was causing e2fsck_set_bitmap_type() to seg fault since
e2fsck_global_ctx was not NULL.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: JP Abgrall <jpa@google.com>
e2fsck: don't use e2fsck_global_ctx in e2fsck_set_bitmap_type()

There is no reason to use e2fsck_global_ctx in
e2fsck_set_bitmap_type(), since we can get the context structure from
fs->priv_data.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
mke2fs: disable resize_inode feature if 64bit feature is enabled

Since auto_64-bit_support is on by default, resize_inode feature will
be disabled when creating a >16T ext4 according to mke2fs.conf(5).

This should also be done when making ext4 with "-O 64bit" to enable
64bit feature explicitly. Otherwise online resize to enlarge a
over-16T fs to larger would fail.

[root@localhost resize]# truncate -s 50t fs.img
[root@localhost resize]# losetup /dev/loop0 fs.img
[root@localhost resize]# mkfs -t ext4 -O 64bit /dev/loop0 30t
[root@localhost resize]# mount /dev/loop0 mnt
[root@localhost resize]# resize2fs /dev/loop0
resize2fs 1.42.7 (21-Jan-2013)
Filesystem at /dev/loop0 is mounted on /root/resize/mnt; on-line resizing required
old_desc_blocks = 3840, new_desc_blocks = 6400
resize2fs: Invalid argument While checking for on-line resizing support

And dmesg shows
[688378.442623] EXT4-fs (loop0): resizing filesystem from 6710886400 to 13421772800 blocks
[688378.443216] EXT4-fs warning (device loop0): verify_reserved_gdb:700: reserved GDT 3201 missing grp 177147 (5804756097)
[688378.443222] EXT4-fs (loop0): resized filesystem to 8858370048
[688378.528451] EXT4-fs warning (device loop0): ext4_group_extend:1710: can't shrink FS - resize aborted

With this fix resize2fs could do the online enlarge correctly.

Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>