Tidyup of error messages, new script to extract error messages.
Error handling stuff, also add forum note to pod, SvREADONLY_on for literals.

Literals now use SvREADONLY_on to stop them getting messed up.

Error messages under construction of new system.
Use error strings rather than format of error from string.
Remove some errors, simplify error handling.
Fix bug in benchmark script vis-a-vis libraries.
whitespace
Add examples directory.
Change literal error to "unexpected character".