Log Message:
Update to calc 2.12.4.0.

User visible changes:

    Fixed a documentation bug for the sgn() builtin.

    Added the 1<<8/2 evaluation example to "help unexpected".  That
    expression evalutes to 128, not 16 as some C programmers might expect.

    Fixed a bug in solve.cal where high was not returned in some situations.

    Fixed a bug reported by Paul & Karen Tomlinson (paulnkaz at pktomlinson
    dot fsnet dot co dot uk) where calling log multiple times with different
    values of epsilon resulted in an incorrect value.

    Fixed a bug where an certains typos (e.g., calling an unknown
    function) would previously cause calc to exit.