Some functions should only return a single match

[sjshuck]

Under the hood, Matchers are always global, but some functions are intended to produce at most one match.

Currently some functions accidentally return multiple matches in unintended ways that don't make sense given the types. Consider that

 {-# LANGUAGE OverloadedStrings #-}

 module Main where

 import Text.Regex.Pcre2

 main :: IO ()
 main = do
     print $ captures "(\\d)(\\d)" "12345"

prints

["12","1","2","34","3","4"]

but should print

["12","1","2"]

[sjshuck]

This is a bug. Fixing it, and providing better docs, will not cause a major version bump.