Merge branch 'lt/case-insensitive'

* lt/case-insensitive:
Make git-add behave more sensibly in a case-insensitive environment
When adding files to the index, add support for case-independent matches
Make unpack-tree update removed files before any updated files
Make branch merging aware of underlying case-insensitive filsystems
Add 'core.ignorecase' option
Make hash_name_lookup able to do case-independent lookups
Make "index_name_exists()" return the cache_entry it found
Move name hashing functions into a file of its own
Make unpack_trees_options bit flags actual bitfields

diff --cc Makefile
Simple merge

diff --cc cache.h
Simple merge

diff --cc config.c
Simple merge

diff --cc dir.c
Simple merge

diff --cc environment.c
Simple merge

diff --cc read-cache.c
Simple merge