issue_6517: Emoji support

Added issue support for the different output types.

- Sources of the emoji
  - based on the Unicode definition v11.0:
    - https://unicode.org/emoji/charts/full-emoji-list.html
    - http://www.unicode.org/emoji/charts/full-emoji-modifiers.html
  - github definition list:
    - https://api.github.com/emojis

- Input of emoji: :<test>: with the restriction that direct after the opening colon and direct before the closing colon no space is allowed
  - doctokinizer.l, adding detection of emoji and new command `\:`
  - doktokinizer.h, adding "word" type  TK_EMOJI
  - docparser.* handling of new "word" type TK_EMOJI (analogous to HTML Entities), handling of new command `\:`
  - cmdmapper,cpp, cmdmapper.h, adding new command `\:`
  - htmlentity.cpp, adding new definition required for new command `\:`

- Emoji
  - emoji.cpp, emoji.h, class for handling emoji analogous to HTML Entities, including small directions on how to update the code when a new emoji is defined. Not everything is converted to lowercase for comparison and accents are removed.
  - doxygen.cpp possibility to create list of supported emoji

- handling emoji for output types (analogous to HTML Entities), see documentation for different output types
  - docparser.h, *docvisitor.*
  - rtfdocvisitor.* converting output to UTF-16 (based on http://scruss.com/blog/2017/03/12/in-the-unlikely-event-you-need-to-represent-emoji-in-rtf-using-perl/)
  - latexdocvisitor.*, handling arguments for emoji in output (see also latexgen.cpp for meaning of the arguments of doxygenemoji).
  - latexgen.cpp, adding new latex command for doxygen (doxygenemoji) and prevent too many open file (code before documentclass)
  - config.xml, definition of `LATEX_EMOJI_DIRECTORY` with path to images required for LaTeX output

- Documentation:
   - emojisup.doc, user description
   - commands.doc, description of new command `\:`
   - index.doc, reference to emoji chapter
   - xmlcmds.doc, adjust reference to next chapter as a new chapter is added
   - Doxyfile*, adding emoji chapter

Build system
  - CMakeLists.txt adding new files

2 files changed, 51 insertions, 0 deletions

diff --git a/src/latexdocvisitor.cpp b/src/latexdocvisitor.cpp
index 452a481..3f90403 100644
--- a/src/latexdocvisitor.cpp
+++ b/src/latexdocvisitor.cpp
@@ -33,6 +33,7 @@
 #include "filedef.h"
 #include "config.h"
 #include "htmlentity.h"
+#include "emoji.h"
 #include "plantuml.h"
 
 const int maxLevels=5;
@@ -210,6 +211,55 @@ void LatexDocVisitor::visit(DocSymbol *s)
   }
 }
 
+void LatexDocVisitor::visit(DocEmoji *s)
+{
+  if (m_hide) return;
+  const char *res_text = EmojiEntityMapper::instance()->text(s->emoji());
+  if (res_text)
+  {
+    const char *res_code = EmojiEntityMapper::instance()->code(s->emoji());
+    m_t << "\\doxygenemoji{";
+    filter(res_text);
+    m_t << "}{";
+    m_t << res_code;
+    m_t << "}{";
+    const char *p = res_code;
+    char res[10];
+    int i = 0;
+    bool first = TRUE;
+    while (*p)
+    {
+      switch(*p)
+      {
+        case '&': case '#': case 'x':
+          break;
+        case ';':
+	  res[i] = '\0';
+	  if (!first) m_t << "-";
+          m_t << res;
+	  first = FALSE;
+          i = 0;
+          break;
+        case '0': case '1': case '2': case '3': case '4':
+        case '5': case '6': case '7': case '8': case '9':
+	  res[i] = *p;
+	  i++;
+          break;
+        case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
+	  res[i] = *p -'a' + 'A'; // so it is uppercase
+	  i++;
+          break;
+      }
+      p++;
+    }
+    m_t << "}";
+  }
+  else
+  {
+    err("LaTeX: non supported Emoji-entity found: %s\n",EmojiEntityMapper::instance()->html(s->emoji()));
+  }
+}
+
 void LatexDocVisitor::visit(DocURL *u)
 {
   if (m_hide) return;
diff --git a/src/xmldocvisitor.h b/src/xmldocvisitor.h
index c65688f..c2c6537 100644
--- a/src/xmldocvisitor.h
+++ b/src/xmldocvisitor.h
@@ -41,6 +41,7 @@ class XmlDocVisitor : public DocVisitor
     void visit(DocLinkedWord *);
     void visit(DocWhiteSpace *);
     void visit(DocSymbol *);
+    void visit(DocEmoji *);
     void visit(DocURL *);
     void visit(DocLineBreak *);
     void visit(DocHorRuler *);