Check for unbalanced parentheses in the current buffer.
More accurately, check the narrowed part of the buffer for unbalanced
expressions ("sexps") in general. This is done according to the
current syntax table and will find unbalanced brackets or quotes as
appropriate. (See Info node `(emacs)Parentheses'.) If imbalance is
found, an error is signaled and point is left at the first unbalanced character.