Try normalizing files to avoid delete/modify conflicts when merging

Try normalizing files to avoid delete/modify conflicts when merging

If a file is modified due to normalization on one branch, and deleted on
another, a merge of the two branches will result in a delete/modify
conflict for that file even if it is otherwise unchanged.

Try to avoid the conflict by normalizing and comparing the "base" file
and the modified file when their sha1s differ.  If they compare equal,
the file is considered unmodified and is deleted.

Signed-off-by: Eyvind Bernhardsen <eyvind.bernhardsen@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>