Location of `Theory' file

[Garrett Wollman]

Back in the mists of ancient time, the rules for time zone names were
stated at the beginning of the `africa' file in tzdata.  At some
point, this explanatory text was moved to the `Theory' file, which
lives in tzcode.  Since many people use only the data and not the
code, I'd like to suggest that the `Theory' file be moved to tzdata so
that it is more closely linked with the information it describes.

-GAWollman