* Add -h and -help options describing the tools and their usage.

* Make the tools compile and run on Windows (MinGW, MSVC).

* Rename project dirs, executables and main source files to more
  meaningful names:
  - Use same base name for project dir, *.pro file, main source file
    and (if applicable) script file.
  - Use the prefix "cplusplus-".
  - The names are now:
      - gen-cpp-ast/generate-ast --> cplusplus-update-frontend
      - mkvisitor --> cplusplus-mkvisitor
      - cplusplus-dump/cplusplus0 --> cplusplus-ast2png

* Get rid of 'c++' shell scripts.

* Get rid of duplicates of 'conf.c++'. Rename to 'pp-configuration.inc'.

* Introduce src/tools/cplusplus-tools-utils containing common stuff
  that is used at least in two tools. 'pp-configuration.inc' can also be
  found here.

* cplusplus-update-frontend:
  - Print file paths of written files to stdout.
  - Convenience: Use default values referencing the appropriate dirs and
    files.

* cplusplus-mkvisitor:
  - Take only one argument, namely the path to AST.h.
  - Convenience: Use default path to AST.h.

* cplusplus-ast2png:
  - Make it run without LD_LIBRARY_PATH.
  - As the name suggests, generate image files in png format (needs
    'dot' from graphviz).
  - Convenience: Read from stdin, which useful for small snippets.

Change-Id: I79c4061fce4a1571c0588dfedd50d4a70715d9df
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>