Maintain and improve error messages

[LaszloLango]

We must check the current error messages.

• Add missing messages
• Use magic string for the same errors
• Provide position information (line:column)
• Add build option to use errors without messages (this can save memory)

[zherczeg]

No need to add magic strings, the compiler should handle the same string merging.

Closing due to inactivity. Please reopen if needed.