Insert the character you type ARG times.
With no ARG, if `skeleton-pair' is non-nil, pairing can occur. If the region
is visible the pair is wrapped around it depending on `skeleton-autowrap'.
Else, if `skeleton-pair-on-word' is non-nil or we are not before or inside a
word, and if `skeleton-pair-filter-function' returns nil, pairing is performed.
Pairing is also prohibited if we are right after a quoting character
such as backslash.
If a match is found in `skeleton-pair-alist', that is inserted, else
the defaults are used. These are (), [], {}, <> and `' for the
symmetrical ones, and the same character twice for the others.
(fn ARG)