Added a bunch of functions.

tests/testmath.jet

@@ -0,0 +1,23 @@
+#!../jet-2.0
+<jet name1="localname" filterblanklines="true" trimlines="true">
+<set name="value1" expr="sin(rad(45))" />
+$[value1]
+<set name="value2" expr="cos(rad(45))" />
+$[value2]
+<set name="value3" expr="rad(30)" />
+$[value3]
+<set name="value4" expr="deg($[value3])" />
+$[value4]
+<set name="value5" expr="asin(rad(45))" />
+$[value5]
+<set name="value6" expr="pow(3, 3)" />
+$[value6]
+<set name="value6" expr="sqrt(49)" />
+$[value6]
+<set name="value7" expr="trunc(49.56)" />
+$[value7]
+<set name="value8" expr="round(49.56)" />
+$[value8]
+<set name="value9" expr="abs(-49.56)" />
+$[value9]
+</jet>