Lexer errors with qualified enum literals and single-character string literals

[manux81]

Problem

While testing STruCpp with a broader IEC 61131-3 Structured Text test suite, I found two lexer issues.

1. Qualified enum literals

Given an enum type such as MachineState, expressions like:

IF Ok THEN
    TestQualifiedEnumLiteral := MachineState#STATE_RUN;
ELSE
    TestQualifiedEnumLiteral := MachineState#STATE_ERROR;
END_IF;

produce:
error: unexpected character: ->#<-

### 2. Single-character string literal
This expression:
```st
Pos := FIND(Result, 'o');
produce:
error: unxpected character: ->'<-


### Impact

_No response_

### Reproduction

[torture_test_core.txt](https://github.com/user-attachments/files/31261191/torture_test_core.txt)

### Code Locations

_No response_

### Fix

_No response_

### Acceptance

Check my attach!