WI #2632 Use correct default encoding for alphanumeric literals written using hex notation

[fm-117]

For #2632 but does not fix it fully yet as we still need a way for the client to override the default value, if need be.

[fm-117]

Converting to draft as i'd like to improve it a bit.

[fm-117]

Ok now we are using the CODEPAGE option to choose the encoding for alphanumeric literals. This is slightly better than a hard-coded default value in source because clients will now have a way to change it, as long as they have control over the TypeCobolOptions instance used by the parser.

We still need:

• to create an option to change the value externally (for LS and CLI users)
• to account for CODEPAGE option declared directly in source: the scanner should read the value and dynamically change the encoding for the rest of the document