Mark M68KArchitectureProvider as immutable
Add tests for M68KArchitectureProvider
Fix a typo in a private method's name
Use SLU.getLogicalLine() in M68KAssemblyContext.initialize()
Report error for UNTIL without DO

Report an assembly error message when an UNTIL directive that is not in
a DO block is encountered (instead of throwing an AssertionError).
HEX: check for the end of an operand properly
Add tests for the HEX directive