Minor improvement in code style in `has_cachedir_tag`.
Use /**/ comments + minor style change
dir_scan.c: Reset directory sizes when excluded by a CACHEDIR.TAG

Tiny bug fix: The size of an excluded directory entry itself should not
be counted, either. This is consistent with what you'd expect: A cache
directory with thousands of files can easily take up several megabytes
for the dir entry - but from the perspective of a backup system that
recognizes cache dirs - the dir is empty, and therefore shouldn't take
any extra space at all.
Merge branch 'master' of git://g.blicky.net/ncdu

Conflicts:
	src/exclude.c