Add #ifndef around all the math macros.

OpenCV defines MIN and MAX. Potentially other libs can too and more.
Sanitize parameters in OpenCV filters.

Some very low parameter values would case a crash inside OpenCV or make
it unresponsive (deadlock or infinite loop - did not check).
Fix broken color parameters in facedetect.

They were all setting the first color!
Add IIRblur source
IIRblur: add range check on float to char
IIRblur: remove unneeded xmmintrin include
Bluescreen0r: map distance parameter to [0,1] range
Bluescreen0r: adapt default and bum minor version
Bluescreen0r: map color parameter to [0,1] range
Bluescreen0r: add explicit color space specification
New Vignette effect.
This effect is not finished yet. (Video card died, ssh-ing the backup now ...) It may even be broken atm :(
Vignetting effect:
* Documentation added
* Value mapping to [0,1] refined
Include vignette in automake build.

Patch by Till Theato.
Corners: fix possible /0 problem
Defish0r: fix possible /0 problem
Test_pat_G: fix possible /0 problem
Saturat0r: set default in constructor
Hueshift0r: use BT 709 luma coeffs
3dflippo: plug a mem leak
Sharpness: plug memory leak