Aribtrary expressions and indexed variable references

This test case it part of the test suite proposed for new devices.

Test case ID: R0259
Language: LD

Code:

tests2/t0259.fbd
    <vars name="A" datatype="BOOL"/>
    <vars name="X" datatype="INT" init="30"/>
    <vars name="Y" datatype="INT" init="2"/>
 (* graphical code omitted in this listing *)