Implement _IIF and fix _ROR & _ROL

[a740g]

This PR introduces _IIF support for QB64-PE, alongside bug fixes and improvements for _ROL and _ROR.

_IIF Implementation:
The _IIF pseudo-function allows for conditional evaluation like the ternary operator in C, with short-circuiting behavior:

result = _IIF(expression, truePart, falsePart)

Key features:

• Only the truePart or falsePart is evaluated, depending on the expression, mimicking C's conditional operator.
• The return type is determined by the type of truePart.
• Both parts cannot mix STRING with other types.

_ROL & _ROR fixes:

1. Resolved an issue where the second argument could incorrectly be a STRING.
2. Simplified the C-side logic using template functions for cleaner code.

Closes #403.