#9514 contents inside of LyX insets with spell check disabled should be ignored by...

#9514 contents inside of LyX insets with spell check disabled should be ignored by spell checker.
The document iterator now skips math insets and insets like notes where spell check is disabled.
The continuous spell checking is part of the row painter drawing and the spell check disabled state
has to be passed down recursively while doing the inset painting.