Collect type information of return values.

Use *one* feedback slot per function for all its return
statements. For assignments, we currently use
several slots per function, because not all
assignments refer to the same variable.

Instead of the variable names, pass the
source location and print the function name.

Add an integration test for --type-profile that checks
for crashes.

Remove type feedback for assignments for now as it convolutes the output.

************ Function with 2 return statements ********
function testFunction(param, flag) {
  // We want to test 2 different return positions in one function.
  if (flag) {
    var first_var = param;
    return first_var;
  }
  var second_var = param;
  return second_var;
}

testFunction({});
testFunction(123, true);
testFunction('hello');
testFunction(undefined);
*******************************************************

************* Sample Output ***************************
Function: testFunction
424: Object
374: number
424: string
424: undefined
*******************************************************

Missing work:
* Handle fall-off returns
* Collect types for parameters
* Remove duplicates from the list of collected types and use a common base class.

BUG=v8:5935

Review-Url: https://codereview.chromium.org/2755973002
Cr-Commit-Position: refs/heads/master@{#43956}