- small fix in Sys.c to compile on Windows:

- small fix in Sys.c to compile on Windows:
   Thanks Florian Eggenberger for telling us about it. And Greg McBride for
   pointing a possible fix.
- Draw.Text and Draw.GetStringWidth updated:
   Now they accept an optional second parameter to set font size and Draw.Text
   returns the drawn string width.
- Partially fixed the update() and PutRaw() bugs in NMesh:
   A total fix will require bigger changes, but what was done (unless buggy)
   takes care of the common cases.