add missing #include <cstdlib>

codeblocks was giving arror :
of\addons\ofxMaxim\libs\maxiMFCC.h|62|error: there are no arguments to
'malloc' that depend on a template parameter, so a declaration of
'malloc' must be available [-fpermissive]|
Merge pull request #20 from Safareli/master

add missing #include <cstdlib>