#259 Range variables as QNames

[Michael Kay]

When a range variable (a variable declared in
for/let/some/every) is namespace-qualified, references
to the variable may not be successfully bound if a
different prefix is used.

Test case: qxmp181

Source code fixed.

In line 1655 of ExpressionParser.java, change

 b.getNameCode()

to

 (b.getNameCode() & 0xfffff)