blkid: add ID_FS_AMBIVALENT for udev output

blkid: add ID_FS_AMBIVALENT for udev output

UI tools that read information from udev need a way how inform users
about ambivalent probing result (more valid filesystems on the
device).

This patch add a new ID_FS_AMBIVALENT variable:

	ID_FS_AMBIVALENT=<info> <info> [ ...]

where <info> is:

	<usage>:<type>[:<version>]

all strings are encoded (white spaces and utf8 are replaced with \hex).

For example:

	# blkid -p -o udev /dev/sda1
	ID_FS_AMBIVALEN=filesystem:vfat:FAT12 other:swap:2

Signed-off-by: Karel Zak <kzak@redhat.com>