fallocate: introduce an option -c to support COLLAPSE_RANGE

Introduce a new option -c (or --collapse-range) to support a new flag
FALLOC_FL_COLLAPSE_RANGE for fallocate(2). It will nullify a particular
range [offset, offset+len] by shifting extents beyond the range to the
beginning of the hole.

Cc: Lukas Czerner <lczerner@redhat.com>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Cc: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: Dongsu Park <dongsu.park@profitbricks.com>
fallocate: add FALLOC_FL_ZERO_RANGE support

Recent Linux kernel supports FALLOC_FL_ZERO_RANGE in fallocate(2).
This patch adds FALLOC_FL_ZERO_RANGE support to fallocate utility,
by introducing a new option -z|--zero-range.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>