Symfony polyfill for intl's grapheme_* functions

 This component provides a partial, native PHP implementation of the Grapheme
 functions from the Intl extension.
 .
  * grapheme_extract: Extract a sequence of grapheme clusters from a
    text buffer, which must be encoded in UTF-8
  * grapheme_stripos: Find position (in grapheme units) of first
    occurrence of a case-insensitive string
  * grapheme_stristr: Returns part of haystack string from the first
    occurrence of case-insensitive needle to the end of haystack
  * grapheme_strlen: Get string length in grapheme units
  * grapheme_strpos: Find position (in grapheme units) of first
    occurrence of a string
  * grapheme_strripos: Find position (in grapheme units) of last
    occurrence of a case-insensitive string
  * grapheme_strrpos: Find position (in grapheme units) of last
    occurrence of a string
  * grapheme_strstr: Returns part of haystack string from the first
    occurrence of needle to the end of haystack
  * grapheme_substr: Return part of a string
 .
 The Symfony Polyfill project backports features found in the latest PHP
 versions and provides compatibility layers for some extensions and functions.
 It is intended to be used when portability across PHP versions and extensions
 is desired.
 .
 Symfony is a PHP framework, a set of tools and a development methodology.