Enclose following ARG sexps in a pair of OPEN and CLOSE characters.
Leave point after the first character.
A negative ARG encloses the preceding ARG sexps instead.
No argument is equivalent to zero: just insert characters
and leave point between.
If `parens-require-spaces' is non-nil, this command also inserts a space
before and after, depending on the surrounding characters.
If region is active, insert enclosing characters at region boundaries.
If arguments OPEN and CLOSE are nil, the character pair is found
from the variable `insert-pair-alist' according to the last input
character with or without modifiers. If no character pair is
found in the variable `insert-pair-alist', then the last input
character is inserted ARG times.
This command assumes point is not in a string or comment.