Takes an optional argument which is the OS name ( as would be returned by $^O ).
By default it will use $^O.
In a scalar context, Will return the decoded content of the hints file suitable for writing straight to a
file handle or undef list if there isnt an applicable hints file for the given or derived
If called in a list context, will return a list, the first item will be the name of the hints file that
will need to be amended, the second item will be a string with the decoded content of the hints file suitable
for writing straight to a file handle. Otherwise an empty list will be returned.