Change the type of m_coef, m_buf1, m_buf2 and registers used inside _process*pass to double
Modify _process*pass functions to comply with Mixxx's coding standards
Minor coding style improvements
Assign fid_design_coef's result directly to m_coef
Merge pull request #270 from badescunicu/bug_1326001

Constant crackling in EngineFilterButterworth8Band::process()