Added emoji extension to Markdown.

This is enabled by default in `markdown_github`.
Added `Ext_emoji` to `Extension` in `Text.Pandoc.Options` (API change).

Closes #2523.

README

@@ -3146,6 +3146,10 @@ treated as spaces or as hard line breaks.  This option is intended for
 use with East Asian languages where spaces are not used between words,
 but text is divided into lines for readability.
 
+#### Extension: `emoji` ####
+
+Parses textual emojis like `:smile:` as Unicode emoticons.
+
 #### Extension: `tex_math_single_backslash` ####
 
 Causes anything between `\(` and `\)` to be interpreted as inline
@@ -3256,7 +3260,7 @@ variants are supported:
 :   `pipe_tables`, `raw_html`, `tex_math_single_backslash`,
     `fenced_code_blocks`, `auto_identifiers`,
     `ascii_identifiers`, `backtick_code_blocks`, `autolink_bare_uris`,
-    `intraword_underscores`, `strikeout`, `hard_line_breaks`,
+    `intraword_underscores`, `strikeout`, `hard_line_breaks`, `emoji`,
     `shortcut_reference_links`.
 
 `markdown_mmd` (MultiMarkdown)

changelog

@@ -5,6 +5,10 @@ pandoc (1.15.2)
 
   * Fixed omitted `url(...)` in CSS data-uri with `--self-contained` (#2489).
 
+  * Added `emoji` Markdown extension, enabled by default in `markdown_github`
+    (#2523).  Added `Ext_emoji` to `Extension` in `Text.Pandoc.Options`
+    (API change).
+
   * `Text.Pandoc.Readers.HTML.parseTags`: Fixed over-eager raw HTML inline
     parsing (#2469).  Tightened up the inline HTML parser so it disallows
     TagWarnings.

pandoc.cabal

@@ -391,6 +391,7 @@ Library
                    Text.Pandoc.Writers.Shared,
                    Text.Pandoc.Asciify,
                    Text.Pandoc.MIME,
+                   Text.Pandoc.Emoji,
                    Text.Pandoc.Parsing,
                    Text.Pandoc.UUID,
                    Text.Pandoc.ImageSize,