better source locations for formal parameters

[msridhar]

Consider the following JS script:

function foo(f,g) {}

When instrumented (with --inlineIID option), we get:

J$.iids = {"9":[1,1,1,21],"17":[1,1,1,21],"25":[1,1,1,21],"33":[1,1,1,21],"41":[1,1,2,1],"49":[1,1,1,21],"57":[1,1,2,1],"65":[1,1,1,21],"73":[1,1,1,21],"81":[1,1,2,1],"89":[1,1,2,1],"nBranches":2,"originalCodeFileName":"/tmp/params.js","instrumentedCodeFileName":"/tmp/params_jalangi_.js"};
jalangiLabel1:
    while (true) {
        try {
            J$.Se(41, '/tmp/params_jalangi_.js', '/tmp/params.js');
            function foo(f, g) {
                jalangiLabel0:
                    while (true) {
                        try {
                            J$.Fe(9, arguments.callee, this, arguments);
                            arguments = J$.N(17, 'arguments', arguments, true, false, false);
                            f = J$.N(25, 'f', f, true, false, false);
                            g = J$.N(33, 'g', g, true, false, false);
...

Note that the source locations for the J$.N callbacks for parameters f and g are [1,1,1,21], i.e., the entirety of function foo. Instead, it would be nice if these callbacks got source locations that only included the corresponding formal parameter (e.g., [1,12,1,13] for parameter f, IID 25).