const_cast problem fix

I don't know what you think about it. I personally find it rather sexy. :-p

Also, I fixed a bug in the script/generated code:
- In getLineBody, you used to do 2 calls to callScintilla with symbolName(v) (SCI_GETLINE in all cases).
It turns out that contrarily to many other calls, callScintilla(SCI_GETLINE, line) won't give you the length of the line. You need to call callScintilla(SCI_GETLINELENGTH, line) instead.