Expose the Bidi_Mirrored table

[LettError]

There is useful information about pairs of mirrored characters. ( <-> ) [ <-> ] etc. It would be great to be able to find a mirrored companion for a character, if it has one.

# This data file lists characters that have the Bidi_Mirrored=Yes property
# value, for which there is another Unicode character that typically has a glyph
# that is the mirror image of the original character's glyph.

http://www.unicode.org/Public/UNIDATA/BidiMirroring.txt