libext2fs: teach the ext2fs_*_block_bitmap_range2() about clusters

The ext2fs_{mark,unmark,test}_block_bitmap2() functions understand
about clusters, and will take block numbers and convert them to
clusters before checking the bitmap.  The
ext2fs_*_block_bitmap_range2() functions did not do this, which made
them inconsistent.  Fortunately, nothing has depended on this
incorrect behavior, and in fact most of the usage of these functions
have only recently been added, and only for optimizations that were
only enabled for non-bigalloc file systems.

So this is a change in previously exported functions, but (a) it
doesn't change the behavior at all for non-bigalloc file systems, and
(b) the change is more likely to fix bugs for bigalloc file systems.
For example, this change fixes a problem with resize2fs and bigalloc
file systems.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
resize2fs: correctly account for clusters when calculating summary stats

Fixes resize2fs so it correctly calculates the number of free clusters
in each block group for file systems with the bigalloc feature
enabled.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
resize2fs: move a cluster at a time with bigalloc file systems

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
contrib: add safe_getenv() support to spd_readdir

This is part of a series of improvements from a 2008 version of
spd_readdir.c that somehow didn't make it into the version which we
checked into e2fsprogs git tree.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
contrib: add thread locking and readdir64_r support to spd_readdir

This is part of a series of improvements from a 2008 version of
spd_readdir.c that somehow didn't make it into the version which we
checked into e2fsprogs git tree.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
contrib: fix namespace leakage in spd_readdir

Declare the internal symbols alloc_dirstruct() and cache_dirstruct()
as static so they don't leak out into the global namespace.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
mke2fs, tune2fs, resize2fs: add warning messages for bigalloc and quota

The bigalloc and quota features have some known issues, so issue
warnings in case users try to use them.

More information can be found here:
	https://ext4.wiki.kernel.org/index.php/Bigalloc
	https://ext4.wiki.kernel.org/index.php/Quota

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Update Release Notes, Changelogs, version.h, for final 1.42.7 release

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>