Replaced DateFromTime and isNaN with macro calls in date code.

src/macros.py

Index: src/macros.py
===================================================================
--- src/macros.py	(revision 2293)
+++ src/macros.py	(working copy)
@@ -113,6 +113,10 @@
 # REGEXP_NUMBER_OF_CAPTURES
 macro NUMBER_OF_CAPTURES(array) = ((array)[0]);
 
+# Gets the value of a Date object. If arg is not a Date object
+# a type error is thrown.
+macro DATE_VALUE(arg) = (%_ClassOf(arg) === 'Date' ? %_ValueOf(arg) : ThrowTypeError());
+
 # Last input and last subject are after the captures so we can omit them on
 # results returned from global searches.  Beware - these evaluate their
 # arguments twice.