add MCN support
check for existance of MCN first
Merge branch 'master' into mcn

This merges the DEBUG flag and printing relevant information to stdout,
rather than stderr.

Conflicts:
	image_id.c
remove typecast for gchar
Merge branch 'mcn' of git://github.com/JonnyJD/image-id

Conflicts:
	image_id.c
Use MIRAGE_MCN_SIZE rather than a magic number