1999-05-12  Jukka-Pekka Iivonen  <iivonen@iki.fi>

        * src/fn-database.c: Database functions accept now string
        criterias too.  In addition, the parsing of criterias and the test
        functions are now public (src/fn-math.c uses these for now on).

        * src/func.h: Added type definitions and function prototypes for
        internal functions that parse and test criterias.

        * src/fn-math.c: Added LN().  Changed LOG() to take an optional
        second parameter.  LOG() returns the logarithm in base 10 if the
        optional argument is not given, otherwise it returns the logarithm
        in the given base.

        * src/fn-math.c: Added COUNTIF() and SUMIF().

        * src/fn-eng.c: Added IMLOG10() and IMLOG2().

        * src/fn-eng.c (complex_ln): Fixed a bug.  Imaginary coefficient
        was calculated incorrectly.