add osx-clang-libc++ flavour to os x formulas

* added poco clang-libc++ recipe
* Todo: add header fix patch to apply @arturoc's changes to the poco headers automatically, if possible.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
clarified some comments

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
add patch for poco headers

this patch should transparently apply the changes @arturoc et al made to the poco headers, whilst retaining upstream compatibility with poco.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
update poco recipe to apply header file patch

* applies patch to header files in copy stage

* add commit hash for poco source so that only approved version of poco source will be checked out.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
add source patch for freeimage

this makes minor adaptions to two  FreeImage source files that allow it to pass through the less permissive clang++ compiler

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
add clang-libc++ formula for FreeImage

Automates everything there is to do to build FreeImage for clang-libc++

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
fix poco header patch

fixes an issue where ofAddListener would not work because header adaptions were missing.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
Merge pull request #7 from openFrameworks-cpp11/cpp11

feature-add osx-clang-libc++ flavour to forumulas