Fixes inconsistencies in declaration of FixedPoint and Interval literals.

Now all follow a what you see is what you get pattern.
Formerly Longs and BigInts would be interpreted as a bit pattern. Now they are handled as the literal value.
Also FixedPoints could not be created from a BigInt, now they can.
Creating literals using the range"range-string" interpolator has been made more robust.
Tests have been added to show the new behavior.