(bug 47268) lang:parseFormattedNumber should return a number, not a string

The documentation, and the expectation of users, is that
lang:parseFormattedNumber() should actually return a number, not a
string.

Bug: 47268
Change-Id: Ieabddd0d9192f1fd8ef7e890d5d6268be9636f38
Merge "(bug 47268) lang:parseFormattedNumber should return a number, not a string"