data: Fixed copying of NULL data.
data_test: Fixed a typo.
data_test: Fixed name/order of the cmp() and strcmp() tests.

;-)
data: Added support for a "regex" data-type.

This type may be used to store the raw and compiled regex in a datum and use
regexes in all places in which a generic value may be used. It does not
support any arithmetic or concatenation operations.
data: Document that regexes are extended, case-insensitive POSIX regexes.