Fix location tracking for for loop expressions

[karoliineh]

Solves #183

The parser now captures distinct location ranges for each component of the for loop, e.g.:

• Initialization: int i = 0
• Condition: i < 5
• Increment: i++

Changes

• Made for_clause grammar rule to return location ranges
• Updated FOR statement to track separate locations for initialization, condition, and increment
• Updated cabs2cil to use the component-specific locations when processing each part
• Updated affected visitor and printer functions