Try to make better diagnostics

[genericptr]

Right now there is a sub standard implementation for diagnostics that doesn't work well enough. CodeTools is simply not good enough as it only returns a single error and stops but maybe we can run the node tree and find errors to show which don't stop the parser (see TCodeToolManager.CheckSyntax).

Some ideas to custom syntax checking:

• Detect if units exist.
• Detect if types or identifiers in code blocks exist.
• Detect invalid mode switches.
• Optional: detect if case is wrong for known identifiers.
• Wrong number of parameters (or types? in function calls (no overloads match)