Merge pull request #285 from pbrunet/Localvariable

Localvariable
Add ast matcher for pattern recognition
Add more generic pattern matching capability
Add generation of classic C loop

* for(int i = x; i < y; i += z)
Add support for real loop with specified step

* If step is computable at compile time, a real loop can be generated.
* It is possible in others case only without omp directive
Improve for generation readability
Add pattern replacement for len_set
Add new pattern modification
Fix distutils tests
Fix pow for numpy array
Reword pattern matching