Make sure all ids in g_linkRefs are lower case

Ids created from the last line were not lower-cased, leading to the link
not being recognized.
Missing & and chars after " in tree of chm documentation

In the chm-doxygen manual we see that for:
- the command \& the & is missing
- commands containing a " all text is missing after this "
These are known limitations of the chm format (see e.g.
http://www.helpware.net/htmlhelp/hhwreadme.htm)
Merge branch 'wip/fix-link-id-on-last-line' of https://github.com/agateau/doxygen into agateau-wip/fix-link-id-on-last-line

Conflicts:
	testing/055/md_055_markdown.xml
	testing/055_markdown.md
Items XML_SCHEMA and XML_DTD declared obsolete

The items XML_SCHEMA and XML_DTD are not used and there is no plan for using them, so declared obsolete.
Merge pull request #106 from albert-github/feature/obsolete_congfig_items

Items XML_SCHEMA and XML_DTD declared obsolete
Error message is given for make distclean as generated_src is a directory

generated_src is a directory and should be removed with the -rf flag.
Similar for other directories like bin, objects, lib, html latex, objects.
Directories man, rtf, perlmod, xml have been added for convenience (when testing with other documentation formats)
Add extra (documenattion) directories to ignore pattern

Add extra (documenattion) directories to ignore pattern
Add docbook directory to be removed as well

Add docbook directory to be removed as well
Better message in case doxygen -u is used

In case of obsolete or not configured entries in the Doxyfile and the option -u is used a message like:
  Warning: Tag `XML_DTD' at line 1821 of file Doxyfile has become obsolete.
  To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
appears, but the item is removed from the Doxyfile.
This patch updates the message (and improves layout) to:
  Warning: Tag `XML_DTD' at line 1821 of file `Doxyfile' has become obsolete.
                  This tag has been removed.
Merge pull request #107 from albert-github/feature/bug_make_rm

Error message is given for make distclean as generated_src is a directory
Merge pull request #109 from albert-github/feature/bug_update_msg

Better message in case doxygen -u is used
Merge pull request #108 from albert-github/feature/extension_gitignore

Add extra (documenation) directories to ignore pattern
detect python2 as Python 2 binary

On some distributions like Arch Linux
"python" is Python 3 and "python2" is Python version 2.

We now try "python2" first and use it if available.
Merge pull request #110 from JonnyJD/python2

detect python2 as Python 2 binary
Bug 723299 - Last line of code block lost if it is only one character and there is no text afterward
Context enhancement
Added basic arithmetic operations to the template expressions, and made the expression lexer faster
More context changes
Added support for elif to the template language
Recognize all HTML4 special character entities

In doxygen a limited number of HTML4 special character entities are recognized, with this patch the full list of HTML4 special character entities (see http://www.w3.org/TR/html4/sgml/entities.html) is supported (as far as they can be represented in the output format).

- doxygen_manual.tex
- latexgen.cpp
  Added wasysym package to support per thousand sign (perthousand command from textcomp didn't work properly)
  Added option for textcomp package so currency symbol would work properly

- htmlcmds.doc
  Adjusted documentation, listing all entities

- compound.xsd
- xmlgen.cpp
  Removed in xsd file all references for special HTML4 character entities and placed placeholder so doxygen (in xmlgen.cpp)can automatically add the right element names.

- util.cpp
- util.h
  Define all entities with their representation for all output formats.
  Define access routines to the different representations
  Mapping (for recognition of the entities) based on running through the list of available entities, after validation of the order of the entities. A few entities contain now besides letters also numbers at the end.

- docparser.h
  Define symbols for all entities as well as a helper struct and enum. The member m_letter is not used anymore and thus removed.
  All existing symbols were renamed so no confusion (i.e. errors when forgetting to rename some symbols) can occur.
  Obsolete references to letter removed, all letters with accents etc. are explicitly defined and not through the generic accent name plus an extra letter.

- docparser.cpp
  Adjust used symbols to their new names.
  Remove references to letter (as used for accents etc.)
  Replace list of explicitly supported entities with call to symbol code access routine.

- docbookvisitor.cpp
- htmldocvisitor.cpp
- latexdocvisitor.cpp
- mandocvisitor.cpp
- perlmodgen.cpp
- printdocvisitor.h
- rtfdocvisitor.cpp
- textdocvisitor.cpp
- xmldocvisitor.cpp
  Replace list of explicitly supported entities with call to access routine and use returned value to output.