db, comparison, ranges: store ranges and comparison instead only one or other

db, comparison, ranges: store ranges and comparison instead only one or other

In the old format something could be stored as a range:

	s32min-10

Or if we couldn't determine any range then it might be stored as a
comparison:

	s32min-[<p0]

But now we want to store the range and the additional limitter:

	s32min-10[<p0]

So if param 0 is 8 then the return range is s32min-7.  If param 0 is 100
then the return range is s32min-10.

Along with that I have cleaned up the str_to_comparison_arg() to not set
and endp pointer.  That wasn't used outside smatch_ranges.  The other
places only care about the parameter and the comparison.

After I updated smatch_db.c to the new format then there weren't any
callers to range_comparison_to_param() so I have removed that function.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>