read-cache: add invalidate parameter to remove_marked_cache_entries

read-cache: add invalidate parameter to remove_marked_cache_entries

When marking cache entries for removal, and later removing them all at
once using 'remove_marked_cache_entries()', cache entries currently
have to be invalidated manually in the cache tree and in the untracked
cache.

Add an invalidate flag to the function.  With the flag set, the
function will take care of invalidating the path in the cache tree and
in the untracked cache.

Note that the current callsites already do the invalidation properly
in other places, so we're just passing 0 from there to keep the status
quo.

This will be useful in a subsequent commit.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>