Updated the lambda coefficient to the one suggested in the original paper (http://www.robots.ox.ac.uk/~joao/publications/henriques_tpami2015.pdf, page 11, Table 2) which works (for me) better then the previous default one.

* Replace OpenMP parallelization with OpenCV's general parallel_for_ to cover other backends than OpenMP.

* Fixed shadowing of range variable in C++11 mode.

Added USING_STD_NAMESPACE macro to text module

bioinspired: prevent call ocl implementation when log sampling is enabled in retina (there is no log sampling kernel)

fixes warning on MacOSX Xcode 8.3.3