Make all accesses to TPJMD5Digest's fields read only

[delphidabbler]

To do this, the public variant record with Bytes, LongWords and A, B, C, & D fields need to be made private and renamed with f prefixes if necessary.

Then new read-only properties named after the fields need to be created with appropriate private read methods that access the fields. These "getters" could be made inline.

[delphidabbler]

As a consequence the new LongWords[] property could be made the default property and Parts[] could be removed.

[delphidabbler]

NOTE

The above changes are API breaking and require a major version number bump.

[delphidabbler]

Getters for the A, B, C & D fields could have (indexed?) getters that simply read from the appropriate fields of the private version of the LongWords array.

[delphidabbler]

As a consequence the new LongWords[] property could be made the default property and Parts[] could be removed

Note that removing Parts[] would be a breaking change.

[delphidabbler]

Note that removing Parts[] would be a breaking change.

Come to think of it, making the fields read only would also be a breaking change, even though there's absolutely no reason for a user to write to them!