fix Issue 8825 - Wrong line number of error message

- Each tokens should have its own 'loc'.
- Rename `Lexer::loc` to `scanloc` to avoid misuse of lookahead-loc.
Fix trivial wrong line number of aggregates
Fix iasm parser bug

`asm_chktok` will advance the token place. So reading `asmtok->uns64value` after the call would take a wrong value.
Merge pull request #2492 from 9rnsr/fix8825

Fix lexer/parser bugs to fix Issue 8825
improve overflow error message
Merge pull request #2580 from WalterBright/improve-msg

improve overflow error message
fix TARGET_CPU=stub, a new CF flag has been added to generic code
Fixes Issue 11088 - Print better diagnostics for enum member overflow errors.
Merge pull request #2581 from AndrejMitrovic/Fix110088

Issue 11088 - Print better diagnostics for enum member overflow errors.