Fix a typo filelist.c:CASE_SENS{A,I}TIVE_FILTER
Better code to parse flags of :substitute
Rename filelist.c:CASE_SENSITIVE_FILTER

To FILTER_DEF_CASE_SENSITIVITY.
Move FILTER_DEF_CASE_SENSITIVITY to filelist.h
Add case_sensitive argument to set_view_filter()
Add i and I flags to :filter command

They control filter case sensitivity:
 - "i" makes filter case insensitive;
 - "I" makes filter case sensitive.

Thanks to filterfalse.
Add flags to the output of :filter? command

Currently they only designate whether non-empty filter is case
sensitive or not.
Merge branch 'add-case-flags-to-filter-cmd'

Add i and I flags to :filter command

They control filter case sensitivity:
- "i" makes filter case insensitive;
- "I" makes filter case sensitive.

Thanks to filterfalse.

Add marks to the output of :filter? command to designate whether
non-empty filter is case sensitive.